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NanoSense Teacher Materials 



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Printed: August 2, 2011 



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next generation textbooks 




Authors 

Patricia Schank, Tina Stanford 



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Contents 



1 Size Matters-Teacher Materials 1 

1.1 Introduction to Nanoscience 1 

2 Clear Sunscreen- Teacher 

Materials 165 

2.1 How Light Interacts with Matter 165 

3 Fine Filters- Teacher Materials 371 

3.1 Filtering Solutions for Clean Water 371 



www.ckl2.org 11 



Chapter 1 



Size Matters- Teacher Materials 



1.1 Introduction to Nanoscience 

Unit Overview 

Contents 

• For Anyone Planning to Teach Nanoscience... Read This First! 

• Size Matters Overview and Learning Goals 

• Unit at a Glance: Suggested Sequencing of Activities by Day for the Full Set of Size Matters Cur- 
riculum Materials 

• Alignment of Unit Activities with Learning Goals 

• Alignment of Unit Activities with Curriculum Topics 

• Alignment Chart: Key Knowledge and Skills 

• (Optional) Size Matters Pretest /Posttest: Teacher Answer Sheet 

For Anyone Planning to Teach Nanoscience... Read This First! 

Nanoscience Denned 

Nanoscience is the name given to the wide range of interdisciplinary science that is exploring the special 
phenomena that occur when objects are of a size between 1 and 100 nanometers (10 -9 m) in at least one 
dimension. This work is on the cutting edge of scientific research and is expanding the limits of our 
collective scientific knowledge. 

Nanoscience is "Science-in-the-Making" 

Introducing students to nanoscience is an exciting opportunity to help them experience science in the mak- 
ing and deepen their understanding of the nature of science. Teaching nanoscience provides opportunities 
for teachers to: 

• Model the process scientists use when confronted with new phenomena 

• Address the use of models and concepts as scientific tools for describing and predicting chemical 
behavior 

• Involve students in exploring the nature of knowing: how we know what we know, the process of 
generating scientific explanations, and its inherent limitations 

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• Engage and value our student knowledge beyond the area of chemistry, creating interdisciplinary 
connections 

One of the keys to helping students experience science in action as an empowering and energizing experience 
and not an exercise in frustration is to take what may seem like challenges of teaching nanoscience and turn 
them into constructive opportunities to model the scientific process. We can also create an active student- 
teacher learning community to model the important process of working collaboratively in an emerging area 
of science. 

This document outlines some of the challenges you may face as a teacher of nanoscience and describes 
strategies for turning these challenges into opportunities to help students learn about and experience 
science in action. The final page is a summary chart for quick reference. 

Challenges &: Opportunities 

1. You will not be able to know all the answers to student (and possibly your own) questions 
ahead of time... 

Nanoscience is new to all of us as science teachers. We can (and definitely should) prepare ahead of time 
using the resources provided in this curriculum as well as any others we can find on our own. However, it 
would be an impossible task to expect any of us to become experts in a new area in such a short period of 
time or to anticipate and prepare for all of the questions that students will ask. 

...This provides an opportunity to model the process scientists use when confronted with 
new phenomena. 

Since there is no way for us to become all-knowing experts in this new area, our role is analogous to the 
"lead explorer" in a team working to understand a very new area of science. This means that it is okay 
(and necessary) to acknowledge that we don't have all the answers. We can then embrace this situation 
to help all of our students get involved in generating and researching their own questions. This is a very 
important part of the scientific process that needs to occur before anyone steps foot in a lab. Each time 
we teach nanoscience, we will know more, feel more comfortable with the process for investigating what 
we don't know, and find that there is always more to learn. 

One strategy that we can use in the classroom is to create a dedicated space for collecting questions. This 
can be a space on the board, on butcher paper on the wall, a question "box" or even an online space if 
we are so inclined. When students have questions, or questions arise during class, we can add them to the 
list. Students can be invited to choose questions to research and share with the group, we can research 
some questions ourselves, and the class can even try to contact a nanoscientist to help us address some of 
the questions. This can help students learn that conducting a literature review to find out what is already 
known is an important part of the scientific process. 

2. Traditional chemistry and physics concepts may not be applicable at the nanoscale level... 

One way in which both students and teachers try to deal with phenomena we don't understand is to go 
back to basic principles and use them to try to figure out what is going on. This is a great strategy as long 
as we are using principles and concepts that are appropriate for the given situation. 

However, an exciting but challenging aspect of nanoscience is that matter acts differently when the particles 
are nanosized. This means that many of the macro-level chemistry and physics concepts that we are used 
to using (and upon which our instincts are based) may not apply. For example, students often want to 
apply principles of classical physics to describe the motion of nanosized objects, but at this level, we know 
that quantum mechanical descriptions are needed. In other situations it may not even be clear if the 
macroscale-level explanations are or are not applicable. For example, scientists are still exploring whether 
the models used to describe friction at the macroscale are useful in predicting behavior at the nanoscale 
(Luan & Robbins, 2005). 

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Because students don't have an extensive set of conceptual frameworks to draw from to explain nanophe- 
nomena, there is a tendency to rely on the set of concepts and models that they do have. Therefore, there 
is a potential for students to incorrectly apply macroscale-level understandings at the nanoscale level and 
thus inadvertently develop misconceptions. 

...This provides an opportunity to explicitly address the use of models and concepts as 
scientific tools for describing and predicting chemical behavior. 

Very often, concepts and models use a set of assumptions to simplify their descriptions. Before applying 
any macroscale-level concept at the nanoscale level, we should have the students identify the assumptions 
it is based on and the situations that it aims to describe. For example, when students learn that quantum 
dots fluoresce different colors based on their size, they often want to explain this using their knowledge 
of atomic emission. However, the standard model of atomic emission is based on the assumption that the 
atoms are in a gaseous form and thus so far apart that we can think about their energy levels independently. 
Since quantum dots are very small crystalline solids, we have to use different models that think about the 
energy levels of the atoms together as a group. 

By helping students to examine the assumptions a model makes and the conditions under which it can be 
applied, we not only help students avoid incorrect application of concepts, but also guide them to become 
aware of the advantages and limitations of conceptual models in science. In addition, as we encounter 
new concepts at the nanoscale level, we can model the way in which scientists are constantly confronted 
with new data and need to adjust (or discard) their previous understanding to accommodate the new 
information. Scientists are lifelong learners and guiding students as they experience this process can help 
them see that it is an integral and necessary part of doing science. 

3. Some questions may go beyond the boundary of our current understanding as a scientific 
community... 

Traditional chemistry curricula primarily deal with phenomena that we have studied for many years and 
are relatively well understood by the scientific community. Even when a student has a particularly deep or 
difficult question, if we dig enough we can usually find ways to explain an answer using existing concepts. 
This is not so with nanoscience! Many questions involving nanoscience do not yet have commonly agreed 
upon answers because scientists are still in the process of developing conceptual systems and theories to 
explain these phenomena. For example, we have not yet reached a consensus on the level of health risk 
associated with applying powders of nanoparticles to human skin or using nanotubes as carriers to deliver 
drugs to different parts of the human body. 

...This provides an opportunity to involve students in exploring the nature of knowing: how 
we know what we know, the process of generating scientific explanations, and its inherent 
limitations. 

While this may make students uncomfortable, not knowing a scientific answer to why something happens 
or how something works is a great opportunity to help them see science as a living and evolving field. 
Highlighting the uncertainties of scientific information can also be a great opportunity to engage students 
in a discussion of how scientific knowledge is generated. The ensuing discussion can be a chance to talk 
about science in action and the limitations on scientific research. Some examples that we can use to begin 
this discussion are: Why do we not fully understand this phenomenon? What (if any) tools limit our ability 
to investigate it? Is the phenomenon currently under study? Why or why not? Do different scientists have 
different explanations for the same phenomena? If so, how do they compare? 

4. Nanoscience is a multidisciplinary field and draws on areas outside of chemistry,such as 
biology, physics, and computer science... 

Because of its multidisciplinary nature, nanoscience can require us to draw on knowledge in potentially 
unfamiliar academic fields. One day we may be dealing with nanomembranes and drug delivery systems, 



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and the next day we may be talking about nanocomputing and semiconductors. At least some of the many 
areas that intersect with nanoscience are bound to be outside our areas of training and expertise. 

...This provides an opportunity to engage and value our student knowledge beyond the 
traditional areas of chemistry. 

While we may not have taken a biology or physics class in many years, chances are that at least some of 
our students have. We can acknowledge students' interest and expertise in these areas and take advantage 
of their knowledge. For example, ask a student with a strong interest in biology to connect drug delivery 
mechanisms to their knowledge about cell regulatory processes. In this way, we share the responsibility for 
learning and emphasize the value of collaborative investigation. Furthermore, this helps engage students 
whose primary area of interest isn't chemistry and gives them a chance to contribute to the class discussion. 
It also helps all students begin to integrate their knowledge from the different scientific disciplines and 
presents wonderful opportunities for them to see the how the different disciplines interact to explain real 
world phenomena. 

Final Words 

Nanoscience provides an exciting and challenging opportunity to engage our students in cutting edge science 
and help them see the dynamic and evolving nature of scientific knowledge. By embracing these challenges 
and using them to engage students in meaningful discussions about science in the making and how we 
know what we know, we are helping our students not only in their study of nanoscience, but in developing 
a more sophisticated understanding of the scientific process. 

References 

• Luan, B., & Robbins, M. (2005, June). The breakdown of continuum models for mechanical contacts. 
Nature 435, 929-932. 

Table 1.1: Challenges of teaching nanoscience and strategies for turning these challenges into 
learning opportunities. 

THE CHALLENGE... PROVIDES THE OPPORTUNITY TO... 

1. You will not be able to know all the answers to Model the process scientists use when confronted 
student (and possibly your own) questions ahead with new phenomena: 

of time Identify and isolate questions to answer 

Work collectively to search for information using 
available resources (textbooks, scientific journals, 
online resources, scientist interviews) 
Incorporate new information and revise previous 
understanding as necessary 
Generate further questions for investigation 

2. Traditional chemistry and physics concepts may Address the use of models and concepts as scien- 
not be applicable at the nanoscale level tific tools for describing and predicting chemical 

behavior: 

Identify simplifying assumptions of the model and 
situations for intended use 

Discuss the advantages and limitations of using 
conceptual models in science 

Integrate new concepts with previous understand- 
ings 

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Table 1.1: (continued) 



THE CHALLENGE... PROVIDES THE OPPORTUNITY TO... 

3. Some questions may go beyond the boundary of Involve students in exploring the nature of know- 
our current understanding as a scientific commu- ing: 

nity How we know what we know 

The limitations and uncertainties of scientific ex- 
planation 

How science generates new information 
How we use new information to change our under- 
standings 

4. Nanoscience is a multidisciplinary field and Engage and value our student knowledge beyond 
draws on areas outside of chemistry, such as bi- the area of chemistry: 

ology and physics Help students create new connections to their ex- 

isting knowledge from other disciplines 
Highlight the relationship of different kinds of in- 
dividual contributions to our collective knowledge 
about science 

Explore how different disciplines interact to explain 
real world phenomena 



Size Matters: Overview and Learning Goals 

Type of Courses: Chemistry, physics, biology, interdisciplinary science 

Grade Levels: 9-12 

Topic Area: The nanoscale perspective of physical properties 

Key Words: Nanoscience, nanotechnology, nanometer, size and scale, properties 

Time Frame: 5-7 class periods (assuming 50 - minutes classes), with extensions 

Overview 

This unit provides an introduction to nanoscience, focusing on concepts related to the size and scale, 
unusual properties of the nanoscale, and example applications of nanoscience. 

Students will participate in learning activities that are designed to help them to establish an understanding 
of the nature of nanoscale science, the relative size of objects, unique properties of nanosized particles, and 
applications of nanoscience. They will read about these issues, complete worksheets, take quizzes, conduct 
laboratory investigations to understand properties of nanoscale objects, and create and present a poster 
comparing a current technology with a related nanotechnology. 

As this is an introductory unit, many new terms will be introduced as students increase their understanding 
of the essential features of nanoscience. References to additional readings and curricular activities are 
provided so that the teacher can choose to include related topics as he or she determines is appropriate. 

Enduring Understandings (EU) 

What enduring understandings are desired? Students will understand: 

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1. The study of unique phenomena at the nanoscale could vastly change our understanding of matter 
and lead to new questions and answers in many areas, including health care, the environment, and 
technology. 

2. There are enormous scale differences in our universe, and at different scales, different forces dominate 
and different models better explain phenomena. 

3. Nanosized materials exhibit some size-dependent effects that are not observed in bulk materials. 

4. New tools for observing and manipulating matter increase our abilities to investigate and innovate. 

Essential Questions (EQ) 

What essential questions will guide this unit and focus teaching and learning? 

1. How small is a nanometer, compared with a hair, a blood cell, a virus, or an atom? 

2. Why are properties of nanoscale objects sometimes different than those of the same materials at the 
bulk scale? 

3. Occasionally, there are advances in science and technology that have important and long-lasting 
effects on science and society. What scientific and engineering principles will be exploited to enable 
nanotechnology to be the next big thing? 

4. How do we see and move things that are very small? 

5. Why do our scientific models change over time? 

6. What are some of the ways that the discovery of a new technology can impact our lives? 

Key Knowledge and Skills (KKS) 

What key knowledge and skills will students acquire as a result of this unit? Students will be able to: 

1. Describe, using the conventional language of science, the size of a nanometer. Make size comparisons 
of nanosized objects with other small objects. 

2. Explain why properties of nanoscale objects sometimes differ from those of the same materials at the 
bulk scale. 

3. Describe an application (or potential application) of nanoscience and its possible effects on society. 

4. Compare a current technology solution with a related nanotechnology-enabled solution for the same 
problem. 

5. Explain how an AFM and a STM work, and give an example of their use. 

Prerequisite Knowledge 

This unit assumes that students are familiar with the following concepts or topics: 

1. Atoms, molecules, cells, cell organelles, and protein molecules. 

2. Basic units of the metric system and knowledge of prefixes. 

3. How to manipulate exponential and scientific notation. 

4. Some knowledge and experience with a light microscope. 

NSES Content Standards Addressed 

K-12 Unifying Concepts and Process Standard 

As a result of activities in grades K-12, all students should develop understanding and abilities aligned 
with the following concepts and processes: (4 of the 5 categories apply) 

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• Systems, order, and organization 

• Evidence, models and explanation 

• Constancy, change, and measurement 

• Form and function 

Grades 9-12 Content Standard A: Science as Inquiry 

Understandings about scientific inquiry 

• Scientists usually inquire about how physical, living, or designed systems function. Con- 
ceptual principles and knowledge guide scientific inquiries. Historical and current scientific knowledge 
influence the design and interpretation of investigations and the evaluation of proposed explanations 
made by other scientists. (12ASI2.1) 

• Scientists rely on technology to enhance the gathering and manipulation of data. New 
techniques and tools provide new evidence to guide inquiry and new methods to gather data, thereby 
contributing to the advance of science. The accuracy and precision of the data, and therefore the 
quality of the exploration, depends on the technology used. (12ASI2.3) 

Grades 9-12 Content Standard B: Physical Science 

Chemical reactions 

• Catalysts, such as metal surfaces, accelerate chemical reactions. Chemical reactions in 
living systems are catalyzed by protein molecules called enzymes. (12BPS3.5) 

Motions and forces 

• Between any two charged particles, electric force is vastly greater than the gravitational 
force. Most observable forces such as those exerted by a coiled spring or friction may be traced to 
electric forces acting between atoms and molecules. (12BPS4.3) 

Grades 9-12 Content Standard E: Science and Technology 

Understanding about science and technology 

• Scientists in different disciplines ask different questions, use different methods of inves- 
tigation, and accept different types of evidence to support their explanations. Many scientific 
investigations require the contributions of individuals from different disciplines, including engineer- 
ing. New disciplines of science, such as geophysics and biochemistry often emerge at the interface of 
two older disciplines. (12EST2.1) 

• Science often advances with the introduction of new technologies. Solving technological 
problems often results in new scientific knowledge. New technologies often extend the current levels 
of scientific understanding and introduce new areas of research. (12EST2.2) 

• Science and technology are pursued for different purposes. Scientific inquiry is driven by 
the desire to understand the natural world, and technological design is driven by the need to meet 
human needs and solve human problems. Technology, by its nature, has a more direct effect on 
society than science because its purpose is to solve human problems, help humans adapt, and fulfill 
human inspirations. 

Technological solutions may create new problems. Science, by its nature, answers questions that may 
or may not directly influence humans. Sometimes scientific advances challenge people's beliefs and 
practical explanations concerning various aspects of the world. (12EST2.4) 

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Grades 9-12 Content Standard F: Science in Personal and Social Perspectives 

Science and technology in local, national, and global challenges 

• Understanding basic concepts and principles of science and technology should precede 
active debate about the economics, policies, politics, and ethics of various science - and technology 
- related challenges. However, understanding science alone will not resolve local, national or global 
challenges. (12FSPSP6.2) 

• Individuals and society must decide on proposals involving new research and the intro- 
duction of new technologies into society. Decisions involve assessment of alternatives, risks, 
costs, and benefits and consideration of who benefits and who suffers, who pays and gains, and what 
the risks are and who bears them. Students should understand the appropriateness and value of basic 
questions - "What can happen?" - "What are the odds?" - and "How do scientists and engineers know 
what will happen? (12FSPSP6.4) 

Grades 9-12 Content Standard G: History and Nature of Science 

Historical perspectives 

• Occasionally, there are advances in science and technology that have important and 
long lasting effects on science and society. Examples of such advances include the following: 
Copernican revolution, Newtonian mechanics, Relativity, Geologic time scale, Plate tectonics, Atomic 
theory, Nuclear physics, Biological evolution, Germ theory, Industrial revolution, Molecular biology, 
Information and communication, Quantum theory, Galactic universe, Medical and health technology. 
(12GHNS3.3) 

AAAS Benchmark Standards 

While some of the content of this unit does not map directly to the NSES, it does address the AAAS 
Benchmarks. Below we list the AAAS Benchmarks that this unit addresses that are not already addressed 
by the NSES. 

Common Themes 

• 11D Scale #1. Representing large numbers in terms of powers of ten makes it easier to think about 
them and to compare things that are greatly different. 

• 11D Scale #2. Because different properties are not affected to the same degree by changes in scale, 
large changes in scale typically change the way that things work in physical, biological, or social 
systems. 

Unit at a Glance: Suggested Sequencing of Activities by Day for the 
Full Set of Size Matters Curriculum Materials 



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Table 1.2: 






Lesson 


Teaching Day 


Main Ac- 


Learning Goals 


Assessment 


Homework 








tivities and 














Materials 










(Prep Day) 


(Refer to 






The Personal 








individual 






Touch: Stu- 








lesson plans 






dent Reading 








for detailed 






and Worksheet 








breakdown) 






Introduction to 
NanoScience: 
Student Read- 
ing 


Introduction to 


1 day 




Class dis- 


EU 1, 4; 


Worksheets 


Visualizing 


Nanoscience 






cussion on 


EQ1, 2, 4, 5, 6; 


for The Per- 


the Nanoscale: 








Personal 


KKS 1, 3 


sonal Touch 


Student Read- 








Touch: Stu- 




and Intro to 


ing 








dent Reading, 




Nanoscience 










Scale Diagram 














Introduction to 














Nanoscience: 














PowerPoint 














and Student 














Worksheet 








Scale of Ob- 


1 day 




Number Line, 


EU2; 


Scale Activity 


Size- 


jects 






Scale of Ob- 


EQ1; 


Worksheets 


Dependent 








jects, or Cut- 


KKS 1 


Scale of Small 


Properties: 








ting It Down 




Objects Quiz 


Student Read- 








Activity 






ing 








Class discus- 














sion and Scale 














Diagram 








Unique 


2 days: 


Day 1 


Unique Prop- 


EU 2, 3; 






Properties at 






erties at the 


EQ 2, 5; 






the Nanoscale 






Nanoscale: 
PowerPoint 
Prepare for 
Unique Prop- 
erties Lab 


KKS 2 








Day 2 




Unique Prop- 
erties Lab 
Activities 
& Student 
Worksheet 




Lab Worksheet 


Seeing and 
Building Small 
Things: Stu- 
dent Reading 



9 



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Table 1.2: (continued) 



Lesson 


Teaching Day 


Main Ac- 
tivities and 
Materials 


Learning Goals 


Assessment 


Homework 


Tools of the 


2 days: Day 1 


Scanning 


EU4; 


Black Box 




Nanosciences 




Probe Mi- 


EQ 4, 5; 


Activity Work- 








croscopy: 


KKS 5 


sheet 








PowerPoint 












Black Box Ac- 












tivity 










Day 2 


Optional Ex- 


EU4; 


Unique Prop- 








tensions for 


EQ4, 5 


erties Quiz 








Exploring 












Nanoscale 












Modeling 








Applications of 


4 days: Day 1 


Applications of 


EU 1; 




Prepare for 


Nanoscience 




Nanoscience: 
PowerPoint 

Assign What's 
New Nanocat 
Poster Session 
topics and 
groups 


EQ 3, 6; 
KKS 3, 4 




What's New 
Nanocat? 
Poster Session 


Applications of 


Days 2-4 


Preparation 




Presentation 




Nanoscience 




for What's 
New NanoCat 
Poster Session 
Group presen- 
tations 




Scoring Rubric 
and Peer 
Feedback Form 





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10 



Table 1.3: 



What enduring understand- 
ings (EU) are desired? Stu- 
dents will understand: 



What essential questions What key knowledge and 

(EQ) will guide this unit and skills (KKS) will students ac- 
focus teaching and learning? quire as a result of this unit? Stu- 

dents will be able to: 



1. The study of unique phe- 
nomena at the nanoscale 
could vastly change our un- 
derstanding of matter and 
lead to new questions and 
answers in many areas, in- 
cluding health care, the en- 
vironment, and technology. 

2. There are enormous scale 
differences in our universe, 
and at different scales, dif- 
ferent forces dominate and 
different models better ex- 
plain phenomena. 

3. Nanosized materials ex- 
hibit some size-dependent 
effects that are not ob- 
served in bulk materials. 

4. New tools for observing 
and manipulating matter 
increase our abilities to in- 
vestigate and innovate. 



1. How small is a nanometer, 
compared with a hair, a 
blood cell, a virus, or an 
atom? 

2. Why are properties of 
nanoscale objects some- 
times different than those 
of the same materials at 
the bulk scale? 

3. Occasionally, there are ad- 
vances in science and tech- 
nology that have important 
and long-lasting effects on 
science and society. What 
scientific and engineering 
principles will be exploited 
to enable nanotechnology 
to be the next big thing? 

4. How do we see and move 
things that are very small? 

5. Why do our scientific mod- 
els change over time? 

6. What are some ways that 
the discovery of a new 
technology can impact our 
lives? 



1. Describe, using the con- 
ventional language of sci- 
ence, the size of a nanome- 
ter. Make size comparisons 
of nanosized objects with 
other small objects. 

2. Explain why properties of 
nanoscale objects some- 
times differ from those of 
the same materials at the 
bulk scale. 

3. Describe an application (or 
potential application) of 
nanoscience and it's possi- 
ble effects on society. 

4. Compare a current tech- 
nology solution with a 
related nanotechnology- 
enabled solution for the 
same problem. 

5. Explain how an AFM and 
a STM work; give an exam- 
ple of their use. 



Alignment of Unit Activities with Learning Goals 



Table 1.4: 



Learning Goals 



Lesson 1: Intro 
to Nanoscience 



Lesson 2: Scale 
of Objects 



Lesson 3: Lesson 4: 

Unique Prop- Tools of the 
erties Nanosciences 



Lesson 5: 

Applic. of 

Nanoscience 



Students will 
understand... 



11 



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Table 1.4: (continued) 



Learning Goals Lesson 1: Intro 


Lesson 2: Scale 


Lesson 


3: 


Lesson 4: 


Lesson 5: 


to Nanoscience 


of Objects 


Unique 


Prop- 


Tools of the 


Applic. of 






erties 




Nanosciences 


Nanoscience 



EU 1. The 

study of 

unique phe- 
nomena at 
the nanoscale 
could vastly 
change our 
understand- 
ing of matter 
and lead to 
new questions 
and answers in 
many areas, in- 
cluding health 
care, the envi- 
ronment, and 
technology. 
EU 2. There 
are enormous 
scale differ- 
ences in our 
universe, and 
at different 
scales, dif- 
ferent forces 
dominate 
and different 
models bet- 
ter explain 
phenomena. 
EU 3. Nano- 
sized materials 
exhibit some 
size-dependent 
effects that are 
not observed in 
bulk materials. 



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12 



Table 1.4: (continued) 



Learning Goals Lesson 1: Intro 


Lesson 2: Scale 


Lesson 


3: 


Lesson 4: 


Lesson 5: 


to Nanoscience 


of Objects 


Unique 


Prop- 


Tools of the 


Applic. of 






erties 




Nanosciences 


Nanoscience 



EU 4. New- 
tools for ob- 
serving and 
manipulat- 
ing matter 
increase our 
abilities to 
investigate and 
innovate. 
Students will 
be able to... 
KKS1. De- 
scribe, using 
the conven- 
tional language 
of science, the 
size of a 
nanometer. 
Make size 
comparisons 
of nanosized 
objects with 



other 
objects. 
KKS2. 
plain 



small 

Ex- 
why 



properties 
of nanoscale 
objects some- 
times differ 
from those 

of the same 
materials at 
the bulk scale. 
KKS3. De- 

scribe an 

application 
(or potential 
application) 
of nanoscience 
and its possi- 
ble effects on 
society. 



13 



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Table 1.4: (continued) 



Learning Goals Lesson 1: Intro 


Lesson 2: Scale 


Lesson 


3: 


Lesson 4: 


Lesson 5: 


to Nanoscience 


of Objects 


Unique 


Prop- 


Tools of the 


Applic. of 






erties 




Nanosciences 


Nanoscience 



KKS4. Com- 
pare a current 
technology 
solution with 
a related 

nanotechnology- 
enabled solu- 
tion for the 
same problem. 
KKS5. Ex- 

plain how an 
AFM and a 
STM work; 
give an exam- 
ple of their 
use. 



Alignment of Unit Activities with Curriculum Topics 



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14 



15 www.ckl2.org 



Table 1.5: (continued) 



Unit Topic 


Chapter Topic 


Subtopic Size 

Lessons 


Matters Specific Materials 


Table 1.5: Chemistry 


Unit Topic 


Chapter Topic 


Subtopic Size 

Lessons 


Matters Specific Materials 



Nature of Chem- Tools of Science 
istry 



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Units & Measure- 




Slides 


ment (size & scale) 


• Lesson 


• 


LI: 1-4 




1 (LI): 


• 


L6: 1-8 




Intro to 
Nanoscience 


Activity /Handout 




• Lesson 2 
(L2): Scale 
of Objects 

• Lesson 6 


• 


LI 

— Student 
Read- 




(L6): One 
Day Intro- 
duction 




ing: 

Intro to 
Nanoscience 

Worksheet: 
Intro to 
Nanoscience 

Handout: 
scale 
dia- 
gram 






• 


L2 

Reading: 
Visu- 
alizing 
the 

Nanoscale 
- Card 
Sort/Number 
Line 
Activ- 
ity 

— Scale of 
Objects 
Activ- 
ity 

— Cutting 
it down 
activity 

— Quiz: 


16 






Scale of 

small 

Objects 



Table 1.5: (continued) 



Unit Topic 



Chapter Topic 



Subtopic 



Size Matters Specific Materials 

Lessons 



Structure of Mat- Electron Configu- Quantum Theory 
ter ration 



• Lesson 

3 (L3): 

Unique 

Properties at the 
nanoscale 



Slides 



L3: 5, 6, 12, 
14 



Structure of Mat- Atomic 
ter tions 



Interac- Chemical Reac- 
tions (precipitate 
formation, self- 
assembly) 



Slides 

Lesson • LI: 17-19 

1 (LI): 

Intro to Activity/Handout 

Nanoscience . Reading . 

Intro to 

Nanoscience 
• Worksheet: 
Intro to 

Nanoscience 



17 



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Table 1.5: (continued) 



Unit Topic 



Chapter Topic 



Subtopic 



Size 
Lessons 



Matters Specific Materials 



Nature of Cheni- Tools of Science 
istry 



Units & Measure- 
ment (size & scale) 



Slides 



(LI) 



Lesson 
1 

Intro to 

Nanoscience 
Lesson 2 

(L2): Scale 
of Objects 
Lesson 6 

(L6): One 
Day Intro- 
duction 



. LI: 


1-4 


. L6: 


1-8 


Activity /Handout 


. LI 






Reading: 




Intro to 




Nanoscience 




Worksheet: 




Intro to 




Nanoscience 




Handout: 




Scale 




Dia- 




gram 


. L2 






Reading: 




Visu- 




alizing 




the 




Nanoscale 




- Card 




Sort /Number 




Line 




Activ- 




ity 




- Scale of 




Objects 




Activ- 




ity 




- Cutting 




it down 




activity 




- Quiz: 




Scale of 




Small 




Objects 



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18 



Table 1.5: (continued) 



Unit Topic 



Chapter Topic 



Subtopic 



Size 
Lessons 



Matters Specific Materials 



Units & Mea- 




Slides 


surement (Instru- 
ments) 


• Lesson 

1 (LI): 


• 
• 


LI: 5-9 
L6: 11-14 




Intro to 
Nanoscience 


Activity /Handout 




• Lesson 2 
(L2): Scale 
of Objects 

• Lesson 


• 


LI 

— Student 
Read- 




4 (L4): 
Tools of 
Nanoscience 




ing: 

Intro to 
Nanoscience 




• Lesson 6 
(L6): One 
Day Intro- 
duction 




Worksheet: 
Intro to 
Nanoscience 

Handout: 
Scale 
Dia- 
gram 






• 


L2 

Reading: 
Visu- 
alizing 
the 

Nanoscale 
— Cutting 
it down 
activity 






• 


L4 

- Black 
Box 

Activ- 
ity 

Reading: 
Seeing 
& 

Build- 
ing 
Small 
Things 

— Quiz 


19 






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Table 1.5: (continued) 



Unit Topic 


Chapter Topic 


Subtopic 


Size 
Lessons 


Matters Specific Materials 








Table 1.6: 


Biology 




Unit Topic 


Chapter Topic 


Subtopic 


Size 
Lessons 


Matters Specific Materials 



Nature of Life 



Science of Biology How 
Work 



Scientists 



Lesson 1 

(LI): Intro- 
duction to 
Nanoscience 



Slides 

. LI: 1-4 

Activity /Handout 

• Scale Di- 
agram: 
Discuss us- 
ing question 
1-2 from 

Intro to 

Nanoscience 
worksheet 



Studying Life 



Lesson 2 

(L2): Scale 
of Objects 



Slides 

. LI: 3 
Activity /Handout 

• Number 
Line 

• Student 
Quiz 

• Reading: Vi- 
sualizing the 
Nanoscale 



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20 



Table 1.6: (continued) 



Unit Topic Chapter Topic Subtopic Size Matters Specific Materials 

Lessons 



Tools and Proce- Slides 

dure 

. Lesson 4 . L4: 1-11, 12 

(L4): Tools (optional) 

Activity /Handout 

• Black Box 
Lab Activity 

• Reading: 
Seeing 

and Build- 
ing Small 
Things 

• Quiz 

Nature of Life The Chemistry of The Nature of Slides 

Life Matter; Properties 

of Water; Carbon * Lesson * L3: 1A7 

Compounds \Jmque ^ Activity /Handout 

Proper- . Reading . 



ties at the 
Nanoscale 



Size- 
Dependent 
Properties 
Unique 
Properties 
Labs 
Student 
Quiz 
Reading: 
The Per- 
sonal Touch 
Reading: 
Intro to 

Nanoscience 



The Human Body Nervous System The Senses Drugs Slides 

and the Nervous L5: 1-2, 

System * Lesson 5 

(L5): Ap- 
plications of 
Nanoscience 



21 www.ckl2.org 



Table 1.6: (continued) 



Unit Topic 



Chapter Topic 



Subtopic 



Size Matters Specific Materials 

Lessons 



The Human Body Circulatory and The Circulatory 
Respiratory Sys- System 
terns 



Lesson 5 

(L5): Ap- 
plications of 
Nanoscience 



Slides 

L5: 1-2, 11 



The Immune Sys- Infectious Disease 
tern and Disease 



Slides 

L5: 1-2, 12 



Cancer 



Slides 

L5: 1-2, 10 



Extensions 



Bioethics 



Use of Nanotech- 
nology in the Hu- 
man Arena 



Size Matters 

• Lesson 5 

(L5): Ap- 
plications of 
Nanoscience 



Any topics cov- 
ered in L5 or any 
students may have 
considered 



Table 1.7: Physics 



Unit Topic 



Chapter Topic 



Subtopic 



Size 
Lessons 



Matters Specific Materials 



Mechanics 



Measurement 



Length/mass/time 
Units/order of 

magnitude 



Lesson 1 

(LI): Intro 
to Nano 
Lesson 2 

(L2): Scale 
of Objects 
Lesson 6 

(L6): One 
Day Intro- 
duction 



Slides 



. LI: 2-3 
. L6: 2-3 

Activity /Handout 



L2 



Card 

Sort/Number 
Line 
Scale 
Dia- 
gram 
Cutting 
it Down 



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22 



Table 1.7: (continued) 



Unit Topic 


Chapter Topic 


Subtopic 




Size 


Matters 


Specific Materials 










Lessons 








Electrostatic 






Slides 






forces 




• 
• 


Lesson 
4 (L4): 
Tools of the 
Nanosciences 
Lesson 6 
(L6): One 
Day Intro- 
duction 


. L4: 2, 8 
. L6: 24 


Electricity 


and Current and Resis- 


Classical 


vs. 






Slides 


Magnetism 


tance 


Modern Physics 
(e.g., different 
dominant forces, 
different "rules" 
at nano/atomic 
scale) 


• 


Lesson 
3 (L3): 
Unique 
Proper- 
ties at the 
Nanoscale 


• L3: (most) 



23 



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www.ckl2.org 24 



Table 1.8: (continued) 



Unit Topic 


Chapter Topic Subtopic Size 

Lessons 


Matters 


Specific Materials 


Table 1.8: Environmental Science 


Unit Topic 


Chapter Topic Subtopic Size 

Lessons 


Matters 


Specific Materials 



Water 



Using Science to What is Science 
Solve Environ- 
mental Problems 



Slides 



Lesson 
1 (LI): 

Intro to 

Nanoscience 
Lesson 2 

(L2): Scale 
of Objects 
Lesson 
3 (L3): 

Unique 
Proper- 
ties at the 
Nanoscale 



. LI: 1-4 

. L3: 1-17 

Activity /Handout 



LI 



L2 



Scale 
Dia- 
gram 
Have 
stu- 
dents 
discuss 
and 
ques- 
tion 
dia- 
gram 
using 
ques- 
tions 
1-2 
from 
student 
work- 
sheet 



Number 
Line 
Student 
Quiz 



25 



Reading: 
Visu- 
alizing 
the 

Nanoscale 
Student 
Quiz 



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Reading: 
Size- 



Table 1.8: (continued) 



Unit Topic Chapter Topic Subtopic Size Matters Specific Materials 

Lessons 



Size Matters Pretest/Posttest: Teacher Answer Sheet 

20 points total 

1. How big is a nanometer compared to a meter? List one object that is nanosized, one that is smaller, 
and one that is larger but still not visible to the naked eye. (1 point each, total of 4 points) 

A nanometer is one billionth of a meter (or 1CT 9 m in scientific notation). 

Sample nanosized objects: 

• Virus, DNA strand (diameter), Ribosome, Hemoglobin, Sucrose molecule 

• Carbon nanotube (diameter), Buckyballs 

• Some enzymes (e.g. ATP synthase), some "molecular motors" (e.g. kinesin) 

• Photosynthetic machinery in plants and bacteria, 

Sample objects that are smaller: 

• Water molecule 

• Atoms 

• Sub-atomic particles (protons, neutrons, electrons) 

Sample objects that are larger than but still not visible to the naked eye: 

• Bacteria, Ameoba 

• Human egg cell, Human sperm cell 

• Red blood cell 

2. Name two properties that can differ for nanosized objects and much larger objects of the same substance. 
For each property, give a specific example. (2 points each, total of 4 points) 

Optical properties (such as color and transparency): 

• Bulk gold appears yellow in color, nanosized gold appears red in color. 

• Regular zinc oxide appear white on the skin, the nano-version appears clear. 

Electrical properties (such as conductivity): 

• Carbon nanotubes conductivity change with diameter, "twist," and number of walls. 

• Physical properties (such as density and boiling point). 

• Nanoparticles have lower melting and boiling points b/c there is a greater percentage of atoms at 
the surface (require less energy to overcome intermolecular attractions). 

Chemical properties (such as reactivities and reaction rates): 
www.ckl2.org 26 



• Nanoparticles have a greater percentage of atoms at the surface and thus greater reactivities (students 
may mention any of the examples of this done in the labs). 

3. Describe two reasons why properties of nanosized objects are sometimes different than those of the same 
substance at the bulk scale. (2 points each, 4 points total) 

Dominance of electromagnetic forces: 

• Gravitational force is a function of mass and distance and is weak between (low-mass) nanosized 
particles. 

• Electromagnetic force is a function of charge and distance is not affected by mass, so it can be very 
strong even when we have nanosized particles. 

Quantum effects: 

• At very small scale, the classical mechanical models that we use to understand matter at the 
macroscale don't work. 

• The quantum mechanical model that does help us understand matter is based on probability, not 
certainty and unusual results such as quantum tunneling (when an electron can "pass through" an 
energy barrier) may occur. 

Surface to volume ratio: 

• As surface area to volume ratio increases, a greater amount of a substance comes in contact with 
surrounding material, this increase reaction rates. 

Random molecular motion: 

• While random molecular motion (molecules moving around in space, rotating around their bonds, 
and vibrating along their bonds) is present for all particles, at the macroscale this motion is very 
small compared to the sizes of the objects and thus is not very influential in how object behave. 

• At the nanoscale however, these motions can be on the same scale as the size of the particles and 
thus have an important influence on how particles behave. 

4. What do we mean when we talk about "seeing" at the nanoscale? (2 points) 

• "Seeing" an object means using a tool that interacts with the object to produce some representation 
of it (often an image). 

• While many common tools use the interaction between visible light and an object to create a repre- 
sentation, at the nanoscale the objects we want to "see" are smaller than the wavelengths of visible 
light so this approach is not useful. 

• To "see" at the nanoscale, we need to use tools that leverage other kinds of interactions with the 
surface of the object (like electrical and magnetic forces) to create a representation of the object. 

5. Choose one technology for seeing at the nanoscale and briefly explain how it works. (3 points) 
Atomic Force Microscope (AFM) 

• Uses a tiny tip that moves in response to the electromagnetic forces between the atoms of the surface 
and the tip. 

27 www.ckl2.org 



• Either measures the tiny upward and downward movement of the tip necessary to remain in close 
contact with the surface or makes the tip vibrate to tap the surface and senses when contacts is 
made. 

• In both bases, the signals (forces or contact) change based on the features of the object's surface 
(height, angle etc.) and are used to infer a topographical image of the object. 

Scanning Tunneling Microscope (STM) 

• Uses a fine tip that can conduct electricity; the nano-object to be imaged must also conduct electricity. 

• The tip is put very near, but not touching the object surface and the "tunneling" of electrons between 
the tip and the atoms of the object's surface being creates a flow of electrons (a current). 

• The signals (current) changes based on the features of the object's surface (height, angle etc.) and 
are used to infer a topographical image of the object. 

6. Describe one application (or potential application) of nanoscience and its possible effects on society. (3 
points) 

Existing Applications Include: 

• Stain Resistant Clothes: Fine-spun fibers ("nanowhiskers") are embedded into fabrics and act like 
peach fuzz to create a cushion of air around the fabric so that liquids bead up and roll off. This 
innovation will leads to less stains, less need for washing clothes (using detergent) and dry cleaning 
(using chemicals), and even less need to replace (and thus produce clothing). These could all have 
positive impacts on the environment. 

• Nano Solar Cells: Traditional solar cells provide one source of clean energy but they are expensive to 
produce. A new kind of solar cells use nanoparticles of 7702 coated with dye molecules to capture the 
energy of visible light and convert it into electricity. These solar cells are less expensive to produce 
and have the potential to be used in a wide range of applications. 

• Clear Sunscreen: Traditional inorganic sunscreens {ZnO and TiO<i) provide powerful protection from 
the full range of UV light, but are often not used or under-applied because they appear white on 
the skin (due to the scattering of visible light). ZnO and 7702 nanoparticles provide the same UV 
protection as their larger counterparts, but are so small that they don't scatter visible light and thus 
appear clear on the skin. 

• Building Smaller Devices and Chips: A technique called nanolithography lets us create much smaller 
devices than current approaches. This technique can be used to further miniaturize the electrical 
components of microchips. Dip pen nanolithography is a 'direct write' technique that uses an AFM 
to create patterns and to duplicate images. "Ink" is laid down atom by atom on a surface, through 
a solvent — often water. 

• Health Monitoring: Several nano-devices are being developed to keep track of daily changes in pa- 
tients' glucose and cholesterol levels, aiding in the monitoring and management of diabetes and high 
cholesterol for better health. For example, some researchers have created coated nanotubes in a way 
that will fluoresce in the presence of glucose. Inserted into human tissue, these nanotubes can be 
excited with a laser pointer and provide real-time monitoring of blood glucose level. 

Potential Applications Include: 

• Paint That Cleans the Air: A titanic-oxide-based compound in nanosized particles has been claimed 
to clean the air by decomposing the major ingredients that cause air pollution such as formaldehyde 
and nitride. This compound could be used in paints, acting as a permanent air purifier and helping 
to improve the air quality in polluted areas. 

www.ckl2.org 28 



"Paint-On" Solar Cells: Scientists are trying to develop a photovoltaic material using semiconducting 

nanorods that can be spread like plastic wrap or paint. These nano solar cells could be integrated 

with other building materials, and offer the promise of cheap production costs that could finally make 

solar power a widely used electricity alternative. 

Drug Delivery Systems: Nanotubes and buckyballs could serve as drug delivery systems. Because 

they are inert and small enough to cross many membranes, including the bloodbrain barrier, they 

could be used to carry reactive drugs to the right part of the body and "deliver" the drug inside the 

appropriate cell. 

Water Treatment: Advanced nanomembranes could be used for water purification, desalination, 

and detoxification, nanosensors could detect contaminants and pathogens, and nanoparticles could 

degrade water pollutants and make salt water and even sewage water easily converted into usable, 

drinkable water. This could help address water crises across the plant. 

Clean Energy: Hydrogen fuel is currently expensive to make, but with catalysts made from nan- 

oclusters, it may be possible to generate hydrogen from water by photocatalytic reactions. Novel 

hydrogen storage systems could be based on carbon nanotubes and other lightweight nanomateri- 

als, nanocatalysts could be used for hydrogen generation, and nanotubes could be used for energy 

transport. 

Detecting Disease with Quantum Dots: Quantum dots are small cadmium-based devices that contain 

a tiny droplet of free electrons, and emit photons when submitted to ultraviolet (UV) light. Scientists 

are exploring ways to seal the dots in polymer capsules to protect the body from cadmium exposure; 

the surface of each capsule can then be designed to attach to different harmful molecules (for example 

those indicating presence of cancer). As the dots collect in a tumor, they become visible in ultraviolet 

light under a microscope, allowing doctors to identify and locate cancer earlier. 



Introduction to Nanoscience 
Teacher Lesson Plan 

Contents 

• Introduction to Nanoscience: Teacher Lesson Plan 

• Introduction to Nanoscience: PowerPoint with Teacher Notes 

• Introduction to Nanoscience Worksheet: Teacher Key 

Orientation 

This lesson is a first exposure to nanoscience for students. The goal is to spark student's interest in 
nanoscience, introduce them to common terminology, and get them to start thinking about issues of size 
and scale. 

• The Personal Touch reading, worksheet and class discussion focus on applications of nanotechnology 
(actual and potential) set in the context of a futuristic story. They are designed to spark student's 
imaginations and get them to start generating questions about nanoscience. 

• The Introduction to Nanoscience reading, PowerPoint slides and worksheet explain key concepts such 
as why nanoscience is different, why it is important, and how we are able to work at the nanoscale. 

• The Scale Diagram shows, for different size scales, the kinds of objects that are found, the tools 
needed to "see" them, the forces that are dominant, and the models used to explain phenomena. 
This diagram will be used throughout the Size Matters Unit. 



29 www.ckl2.org 



Refer to the "Challenges and Opportunities" chart at the beginning of the unit before starting this lesson. 
Tell students that although making and using products at the nanoscale is not new, our focus on the 
nanoscale is new. We can gather data about nanosized materials for the first time because of the availability 
of new imaging and manipulation tools. You may not know all of the answers to the questions that students 
may ask. The value in studying nanoscience and nanotechnology is to learn how science understanding 
evolves and to learn science concepts. 

Essential Questions (EQ) 

What essential questions will guide this unit and focus teaching and learning? 

(Numbers correspond to learning goals overview document) 

1. How small is a nanometer, compared with a hair, a blood cell, a virus, or an atom? 

2. Why are properties of nanoscale objects sometimes different than those of the same materials at the 
bulk scale? 

4. How do we see and move things that are very small? 

5. Why do our scientific models change over time? 

6. What are some of the ways that the discovery of a new technology can impact our lives? 
Enduring Understandings (EU) 

Students will understand: 

(Numbers correspond to learning goals overview document) 

1. The study of unique phenomena at the nanoscale could change our understanding of matter and lead 
to new questions and answers in many areas, including health care, the environment, and technology. 

4. New tools for seeing and manipulating increase our ability to investigate and innovate. 

Key Knowledge and Skills (KKS) 

Students will be able to: 

(Numbers correspond to learning goals overview document) 

1. Describe, using the conventional language of science, the size of a nanometer. Make size comparisons 
of nanosized objects with other small sized objects. 

3. Describe an application (or potential application) of nanoscience and its possible effects on society. 
Prerequisite Knowledge and Skills 

• Familiarity with atoms, molecules and cells. 

• Knowledge of basic units of the metric system and prefixes. 

• Ability to manipulate exponential and scientific notation. 

• Some knowledge of the light microscope. 

Related Standards 

. NSES Science and Technology: 12EST2.1, 12EST2.2 

. NSES Science as Inquiry: 12ASI2.3 

. AAAS Benchmarks: 11D Scale #1, 11D Scale #2 



www.ckl2.org 30 



Table 1.9: 



Day 



Activity 



Time 



Materials 



Prior to this lesson 



Homework: The Per- 
sonal Touch: Reading & 
Student Worksheet 
Homework: Introduc- 
tion to Nanoscience: 
Reading & Student 
Worksheet 



30 min 
40 min 



Photocopies of readings 
and worksheets: 
The Personal Touch 
Introduction to 

Nanoscience 



Day 1 (50 min) 



Use The Personal Touch 
reading & worksheet as 
a basis for class discus- 
sion. Identify and dis- 
cuss some student ques- 
tions from the work- 
sheet. 

Show the Introduction 
to Nanoscience: Pow- 
erPoint Slides, using 
teacher's notes as talk- 
ing points. Describe 
and discuss: 

• The term 
"nanoscience" 
and the unit 
"nanometer" 

• The tools of 
nanoscience 

• Examples of nan- 
otechnology 



15 min 



20 min 



Introduction to 

Nanoscience: Pow- 

erPoint Slides 
Computer and projector 



Hand out Scale Dia- 5 min 
gram and explain the 
important points repre- 
sented on it. Tell stu- 
dents to keep the hand- 
out since it will be used 
throughout the unit. 
In pairs, have students 5 min 
review answers to Intro- 
duction to NanoScience: 
Student Worksheet 
Return to whole class 5 min 
discussion for questions 
and comments. 



Photocopies of Scale Di- 
agram 



31 



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Introduction to Nanoscience 




What's happening lately at a very, very small scale 
What is Nanoscale Science? 




Figure 1.1 



• The study of objects and phenomena at a very small scale, roughly 1 to 100 nanometers(nm) 

— 10 hydrogen atoms lined up measure about 1 nm 

— A grain of sand is 1 millionnm, or 1 millimeter, wide 

• An emerging, interdisciplinary science involving 

— Physics 

— Chemistry 

— Biology 

— Engineering 

— Materials Science 

— Computer Science 

How Big is a Nanometer? 

• Consider a human hand 



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32 




■ I i ■ \J I : 



1 f. l.ifTCtCf \ 




*r:e 



nar^scale 



Figure 1.2 



Are You a Nanobit Curious? 



• What's interesting about the nanoscale? 

— Nanosized particles exhibit different properties than larger particles of the same substance 

• As we study phenomena at this scale we... 

— Learn more about the nature of matter 

— Develop new theories 

— Discover new questions and answers in many areas, including health care, energy, and technology 

— Figure out how to make new products and technologies that can improve people's lives 

So How Did We Get Here? 

New Tools! 

As tools change, what we 

canseeanddochanges 

Using Light to See 

• The naked eye can see to about 20 microns 

— A human hair is about 50 - 100 microns thick 

• Light microscopes let us see to about 1 micron 

— Bounce light off of surfaces to create images 

Using Electrons to See 

• Scanning electron microscopes (SEMs), invented in the 1930s, let us see objects as small as 10 nanometers 

— Bounce electrons off of surfaces to create images 



33 



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Light microscope 
(magnification up to 1000x) 






to see red blood cells 
(400x) 




Figure 1.3 




Greater resolution to see things like blood cells in greater detail 



Figure 1.4 



Higher resolution due to small size of electrons 



Touching the Surface 




This is about how big atoms are 
compared with the tip of the 
microscope 

Figure 1.5 



Scanning probe microscopes, developed in the 1980s, give us a new way to "see" at the nanoscale 
We can now see really small things, like atoms, and move them too! 



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34 



Scanning Probe Microscopes 

• Atomic Force Microscope (AFM) 

— A tiny tip moves up and down in response to the electromagnetic forces between the atoms 
of the surface and the tip 

— The motion is recorded and used to create an image of the atomic surface 

• Scanning Tunneling Microscope (STM) 

— A flow of electrical current occurs between the tip and the surface 

— The strength of this current is used to create an image of the atomic surface 

So What? 

Is nanoscience just seeing and moving really small things? 

• Yes, but it's also a whole lot more. Properties of materials change at the nanoscale! 
Is Gold Always "Gold"? 




- 




-* — 7 



/ 

WW ' 



n 






f\ 



Figure 1.6 

Cutting down a cube of gold 

— If you have a cube of pure gold and cut it, what color would the pieces be? 



35 



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Now you cut those pieces. What color will each of the pieces be? 

If you keep doing this - cutting each block in half - will the pieces of gold always look "gold"? 



Nanogold 




12 nm gold particles look red 



Other sizes are other colors 

■ ■ ■ ■ ■ 

■ ■ i ■ i 




Figure 1.7 



Well... strange things happen at the small scale 

— If you keep cutting until the gold pieces are in the nanoscale range, they don't look gold any- 
more... They look RED! 

— In fact, depending on size, they can turn red, blue, yellow, and other colors 



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36 



. Why? 

— Different thicknesses of materials reflect and absorb light differently 

Nanostructures 

What kind of nanostructures can we make? 
What kind of nanostructures exist in nature? 
Carbon Nanotubes 




Model of a carbon nanotube 



Figure 1.8 



• Using new techniques, we've created amazing structures like carbon nanotubes 

— 100 time stronger than steel and very flexible 

— If added to materials like car bumpers, increases strength and flexibility 

Carbon Buckyballs (C60) 

• Incredible strength due to their bond structure and "soccer ball" shape 

• Could be useful "shells" for drug delivery 

— Can penetrate cell walls 

— Are nonreactive (move safely through blood stream) 

Biological Nanomachines in Nature 



Life begins at the nanoscale 



37 



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Model of Buckminsterfullerene 

Figure 1.9 

— Ion pumps move potassium ions into and sodium ions out of a cell 

— Ribosomes translate RNA sequences into proteins 

— Viruses infect cells in biological organisms and reproduce in the host cell Influenza virus 

Building Nanostructures 

How do you build things that are so small? 
Fabrication Methods 

• Atom-by-atom assembly 

— Like bricklaying, move atoms into place one at a time using tools like the AFM and STM 

• Chisel away atoms 

— Like a sculptor, chisel out material from a surface until the desired structure emerges 

• Self assembly 

— Set up an environment so atoms assemble automatically. Nature uses self assembly (e.g., cell 
membranes) 

Example: Self Assembly By Crystal Growth 

• Grow nanotubes like trees 

— Put iron nanopowder crystals on a silicon surface 

— Put in a chamber 

www.ckl2.org 38 








Influenza virus 



Figure 1.10 



39 



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IBM logo assembled 
from individual xenon 
atoms 




Polystyrene 

spheres selfassembling 



Figure 1.11 




Growing a forest of nanotubes! 



Figure 1.12 



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40 



— Add natural gas with carbon (vapor deposition) 

— Carbon reacts with iron and forms a precipitate of carbon that grows up and out 

• Because of the large number of structures you can create quickly, self-assembly is the most important 
fabrication technique 

Teacher Notes 

Overview 

This series of slides introduces students to what nanoscience is, how big is a nanometer, various types of 
microscopes used to see small things, some interesting nanostructures, and interesting properties of these 
structures. 

Slide 1: Introduction to Nanoscience 

Explain to students that you're going to explain what nanoscience is and how we see small things, give a 
few examples of interesting structures and properties of the nanoscale, and describe how scientists build 
very small structures. 

Slide 2: What is Nanoscale Science? 

Nanoscale science deals with the study of phenomena at a very small scale -1CT 7 m (100 nm) to 10~ 9 m (1 nm) 
where properties of matter differ significantly from those at larger scales. This very small scale is difficult 
for people to visualize. There are several sizeand scale-related activities as part of the NanoSense materials 
that you can incorporate into your curriculum that help students think about the nanoscale. 

This slide also highlights that nanoscale science is a multidisciplinary field and draws on areas outside 
of chemistry, such as biology, physics, engineering and computer science. Because of its multidisciplinary 
nature, nanoscience may require us to draw on knowledge in potentially unfamiliar academic fields. 

Slide 3: How Big is a Nanometer? 

This slide gives a "powers of ten" sense of scale. If you are running the slides as a PowerPoint presentation 
that is projected to the class, you could also pull up one or more powers of ten animations. See http: 
//micro. magnet .fsu.edu/primer/java/scienceopticsu/powersof 10 for a nice example that can give 
students a better sense of small scale. 

As you step through the different levels shown in the slide, you can point out that you can see down to about 
#3 (1000 microns) with the naked eye, and that a typical microscope as used in biology class will get you 
down to about #5 (10 microns). More advanced microscopes, such as scanning electron microscopes can 
get you pretty good resolution in the #6 (1 micron) range. Newer technologies (within the last 20 years or 
so) allow us to "see" in the #7 (100 nanometer) through #9 (1 nanometer) ranges. These are the scanning 
probe and atomic force microscopes. 

Slide 4: Are You a Nanobit Curious? 

This slide highlights why we should care about nanoscience: It will change our lives and change our 
understanding of matter. A group of leading scientists gathered by the National Science Foundation in 
1999 said: "The effect of nanotechnology on the health, wealth and standard of living for people in this 
century could be at least as significant as the combined influences of microelectronics, medical imaging, 
computer-aided engineering and man-made polymers developed in the past century." (Accessed August, 
2005, from http: //www. techbizf 1 . com/news_desc . asp?article_id=1792.) 

Slide 5: So How Did We Get Here? 

This slide denotes the beginning of a short discussion of the evolution of imaging tools (i.e. microscopes). 
One of the big ideas in science is that the creation of tools or instruments that improve our ability to 

41 www.ckl2.org 



collect data is often accompanied by new science understandings. Science is dynamic. Innovation in 
scientific instruments is followed by a better understanding of science and is associated with creating 
innovative technological applications. 

Slide 6: Using Light to See 

You may want to point out that traditional light microscopes are still very useful in many biology-related 
applications since things like cells and bacteria can readily be seen with this tool. They are also fairly 
inexpensive and are easy to set up. 

Slide 7: Using Electrons to See 

Point out that the difference between the standard light microscope and the scanning electron microscope 
is that electrons, instead of various wavelengths of light, are "bounced" off the surface of the object being 
viewed, and that electrons allow for a higher resolution because of their small size. You can use the analogy 
of bouncing bb's on a surface to find out if it is uneven (bb's scattering in all different directions) compared 
to using beach balls to do the same job. 

Slide 8: Touching the Surface 

Point out how small the tip of the probe is compared to the size of the atoms in the picture. Point out 
that this is one of the smallest tips you can possibly make, and that it has to be made from atoms. Also 
point out that the tip interacts with the surface of the material you want to look at, so the smaller the 
tip, the better the resolution. But because the tip is made from atoms, it can't be smaller than the atoms 
you are looking at. Tips are made from a variety of materials, such as silicon, tungsten, and even carbon 
nanotubes. 

Slide 9: Scanning Probe Microscopes 

Point out the difference between the AFM and the STM: the AFM relies on movement due to the 
electromagnetic forces between atoms, and the STM relies on electrical current between the tip and the 
surface. Mention that the AFM was invented to overcomes the STM's basic drawback: it can only be used 
to sense the nature of materials that conduct electricity, since it relies on the creation of a current between 
the tip and the surface. The AFM relies on actual contact rather than current flow, so it can be used to 
probe almost any type of material, including polymers, glass, and biological samples. 

Point out that the signals (forces or currents) from these instruments are used to infer an image of the 
atoms. The tip's fluctuations are recorded and fed into computer models that generate images based on 
the data. These images give us a rough picture of the atomic landscape. 

Slide 10: So What? 

The following slides will give examples to help illustrate why we care about seeing and moving things at a 
very small scale. What makes the science at the nanoscale special is that at such a small scale, different 
physical laws dominate and properties of materials change. 

Slide 11: Is Gold Always Gold? 

Help students think about what happens when you keep cutting something down. At what point will you 
get down to the individual atoms, and at what point does "color" change and go away? Remind them that 
individual atoms do not have color. The color of a substance is determined by the wavelength of the light 
that bounces off it, and one atom is too small to reflect light on its own. Only once you have an aggregate 
(a bunch) of atoms big enough can you begin to discern something approaching "color." For example, a 
bunch of salt crystals together look white, but an individual salt crystal is colorless. 

Slide 12: Nanogold 

Prompt your students to look at their jewelry, etc. and think about color of materials. Use analogies to 
drive home the concept that different thicknesses of a material can produce different colors. For example, 

www.ckl2.org 42 



oil on water produces different colors based on how thin the film of oil is. In an oil slick the atoms aren't 
changing; there are just different thicknesses (numbers of atoms) reflecting different colors. Leaves on a 
tree look green because the atomic structure on surface of leave reflects back green wavelength and absorbs 
all others. As leaves die, the atomic structure changes so you get brown reflected back as the chlorophyll 
breaks down. 

For gold, color is based on the crystalline or atomic structure at the nanoscale: light absorbs differently 
based on the thickness of the crystal. In the Personal Touch story, Sandra's dress changes color because 
she can change the arrangement of atoms in her dress, which will then reflect different colors. 

Slide 13: Nanostructures 

The next few slides provide examples of what kind of nanostructures scientists can create and nanostruc- 
tures that exist in nature. 

Slide 14: Carbon Nanotubes 

This slide describes a recently-created structure that has some amazing properties. Nanotubes are very 
light and strong and can be added to various materials to give them added strength without adding much 
weight. Nanotubes also have interesting conductance (electrical) properties. 

Slide 15: Carbon Buckyballs 

Buckyballs are another very strong structure based on its interlaced "soccer ball" shape. It has the unique 
property of being able to carry something inside of it, penetrate a cell wall, and then deliver the package 
into the cell (not sure how you "open" the buckyball!). It is also non-reactive in general in the body, so 
your body will not try to attack it and it can travel easy in the bloodstream. 

Slide 16: Biological Nanomachines in Nature 

There are many natural nanoscale devices that exist in our biological world. Life begins at the nanoscale! 
For example, inside all cells, molecules and particles of various sizes have to move around. Some molecules 
can move by diffusion, but ions and other charged particles have to be specifically transported around cells 
and across membranes. Biology has an enormous number of proteins that self- assemble into nanoscale 
structures. See the "Introduction to Nanoscience: Student Reading" for more examples. 

Slide 17: Building Nanostructures 

The next two slides provide examples of how we build things that are so small. 

Slide 18: Fabrication Methods 

This slide summarizes the three main methods that are used to make nanoscale structures. First, the tips 
of scanning probe microscopes can form bonds with the atoms of the material they are scanning and move 
the atoms. Using this method with xenon atoms, IBM created the tiniest logo ever in 1990. Alternately, 
scientists can chisel out material from the surface until the desired structure emerges. This is the process 
that the computer industry uses to make integrated circuits. Finally, self assembly is the process by which 
molecular building blocks "assemble" naturally to form useful products. Molecules try to minimize their 
energy levels by aligning themselves in particular positions. If bonding to an adjacent molecule allows for 
a lower energy state, then the bonding will occur. We see this happening in many places in nature. For 
example, the spherical shape of a bubble or the shape of snowflake are a result of molecules minimizing 
their energy levels. See the "Introduction to Nanoscience: Student Reading" for more information. 

Slide 19: Example: Self Assembly By Crystal Growth 

One particular type of self-assembly is crystal growth. This technique is used to "grow" nanotubes. In this 
approach, "seed" crystals are placed on some surface, some other atoms or molecules are introduced, and 
these particles mimic the pattern of the small seed crystal. For example, one way to make nanotubes is to 
create an array of iron nanopowder particles on some material like silicon, put this array in a chamber, and 

43 www.ckl2.org 



add some natural gas with carbon to the chamber. The carbon reacts with the iron and supersaturates it, 
forming a precipitate of carbon that then grows up and out. In this manner, you can grow nanotubes like 
trees! 

Teacher Key 

Below is a set of questions to answer during and/or following the introduction to nanoscience slide presen- 
tation. 

1. What is the range of the "nanoscale"? 

Roughly 1 to 100 nanometers (nm) in at least one dimension. 

2. What is the smallest size (in meters) that the human eye can see? 

The naked eye can see down to about 20 microns (micrometers). One micron is 10 -6 meters, so ten microns 
is 10 -5 meters, and 20 microns is 2 x 10 -5 meters. That's 20 millionths of a meter. 

3. How much more "power" can a light microscope add to the unaided eye? In other words, 
what is the smallest resolution that a light microscope can show? 

Light microscopes let us see to about 1 micron, or 10 -6 meters. That's 20 times smaller than the eye can 
see on its own. 

4. Briefly describe how light microscopes and electron microscopes work. 

Light microscopes "bounce" visible light of off surfaces to create images. Electron microscopes "bounce" 
electrons off of surfaces to create images. (Electron microscopes provide higher resolution because electrons 
are so small, i.e., smaller than a wavelength of visible light.) 

5. Name one of the new microscopes that scientists have used to view objects at the nanoscale 
and explain how that microscope allows you to view objects. 

The scanning tunneling microscope (STM) and the atomic force microscope (AFM) are both new scanning 
probe microscopes (SPM) that can be used to view objects at the nanoscale. 

STM: A flow of electrical current occurs between the tip of the microscope probe and the surface of the 
object. The variation in strength of this current due to the shape of the surface is used to form an image. 

AFM: The tip of the microscope probe moves in response to electromagnetic forces between it and the 
atoms on the surface of the object. As the tip moves up and down, the movement is used to form an image. 

6. Give a short explanation of why the nanoscale is "special." 

Nanosized particles exhibit different properties than larger particles of the same substance. Studying 
phenomena at this scale can improve and possibly change our understanding of matter and lead to new 
questions and answers in many areas. 

7. Name one example of a nanoscale structure and describe its interesting properties. 

Examples given in the slides: (1) Carbon nanotubes are 100 time stronger than steel, yet very flexible. (2) 
Carbon buckyballs can pass through cell membranes and be used for drug delivery. 

Scale of Objects 

Contents 

• Scale of Objects: Teacher Lesson Plan 

• Number Line/Card Sort Activity: Teacher Instructions & Key 

www.ckl2.org 44 



• Cutting it Down Activity: Teacher Instructions & Key 

• Scale of Objects Activity: Teacher Key 

• Scale of Small Objects Quiz: Teacher Key 

Teacher Lesson Plan 

Orientation 

This lesson helps students think about the enormous scale differences in our universe. There are three 
classroom activities that you can choose between and combine. 

• The Student Reading on Visualizing the Nanoscale reviews common size units and provides several 
examples to help students imagine the nanoscale. 

• The Number Line/Card Sort Activity has students place objects along a scale and reflect on the size 
of common objects in relation to each other. 

• The Scale of Small Objects Activity/Worksheet has students identify the size scale of objects with 
less focus on their relation to each other. 

• The Cutting It Down Activity has students cut a strip of paper in half as many times as possible 
and focuses on tools and their precision at different scales. 

• The Scale of Small Objects Quiz tests the absolute and relative size of objects. 

Essential Questions (EQ) 

What essential questions will guide this unit and focus teaching and learning? 

(Numbers correspond to learning goals overview document) 

1. How small is a nanometer, compared with a hair, a blood cell, a virus, or an atom? 
Enduring Understandings (EU) 

Students will understand: 

(Numbers correspond to learning goals overview document) 

2. There are enormous scale differences in our universe, and at different scales, different forces dominate 
and different models better explain phenomena. 

Key Knowledge and Skills (KKS) 

Students will be able to: 

(Numbers correspond to learning goals overview document) 

1. Describe, using the conventional language of science, the size of a nanometer. Make size comparisons 
of nanosized objects with other small sized objects. 

Prerequisite Knowledge and Skills 

• Familiarity with atoms, molecules and cells. 

• Knowledge of basic units of the metric system and prefixes. 

• Ability to manipulate exponential and scientific notation. 

Related Standards 

. NSES Science as Inquiry: 12ASI2.3 
. AAAS Benchmarks: 11D Scale #1 



45 www.ckl2.org 



Table 1.10: 



Day 



Activity 



Time 



Materials 



Prior to this lesson 



Day 1 (40 min) 



Homework: Reading & 30 min 
Worksheet: Visualizing 
the Nanoscale 

Use Visualizing the 10 min 
Nanoscale: Student 

Reading as a basis for 
class discussion and stu- 
dent questions. Use the 
Scale Diagram: Dom- 
inant Objects, Tools, 
Models, and Forces at 
Various Different Scales 
as a reference. 

Number Line/Card Sort 20 min 
Activity 
or 

Cutting it Down Activ- 
ity 
or 

Scale of Objects Activ- 
ity 



Photocopies of Visualiz- 
ing the Nanoscale: Stu- 
dent Reading 
Students will refer to 
the Scale Diagram 
handout; photocopy it 
if not previously handed 
out. 



Photocopies of Number 
Line/Card Sort Activ- 
ity: Student Instruc- 
tions &; Worksheet 
A set of cards (ob- 
jects and units) for each 
small group of students 
(consider printing cards 
on card stock for reuse) 
Photocopies of Cut- 
ting It Down Activity: 
Student Instructions & 
Worksheet 
Strips of Paper 
Scissors 

Photocopies of Scale 
of Objects Activity: 
Student Instructions & 
Worksheet 



Return to whole class 5 min 

discussion for questions 

and comments 

Scale of Small Objects: 5 min 

Student Quiz 



Photocopy Scale of 
Small Objects: Student 
Quiz 

Teacher Key for correct- 
ing Student Quiz 



Number Line/Card Sort Activity: Teacher Instructions &; Key 



Overview 

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46 



In this activity, your students will explore their perception of the size of different objects. Have your 
students form into pairs or small groups, and give each group the Number Line/Card Sort Activity: 
Student Instructions & Worksheet handout and two sets of cards: one with objects on them and one with 
units on them. Their task is to create a number line and place the cards at the appropriate places on the 
number line. 

You may also want to discuss with your students why we are using powers of 10 for the units in this exercise 
instead of using a "regular" linear scale (e.g., a meter stick). Here are some questions and issues you may 
want to bring up: 

The number line units are powers of 10; that is, they are a base 10 logarithmic scale. Why don't we just 
use a linear scale, like a meter stick? Using a linear scale, we could easily mark off 1 meter, 1 cm, and 
1 mm. But it's hard to mark (or see) smaller than that. Plus, most of the cards (for small objects) would 
pile up on top of each other! 

Instead, we'd like to spread our cards out to clearly see which objects are bigger or smaller than others. 
We can do this if we use a logarithmic scale. The word logarithm is a synonym for the words "exponent" 
or "power." Powers of 10 use a base 10 logarithm scale. In base 10, Log 10 (10 -10 ) = -10. So, each card 
unit represents an exponent (-10, -9, -8 ... - 1, 0) of 10. These are integers that are equidistant from each 
other. 

Materials 

• Cards for the objects 

• Cards for the units, in powers of 10 meters 

Instructions 

On a surface like a lab table, order the cards for powers of 10 in a vertical column, with the largest at the 
top and the smallest at the bottom. Space the cards equidistant from each other, leaving a gap between 
the cards for 10 -10 and 10 -15 . This is your number line. 

Next, place each object next to the closest power of 10 in the number line that represents the size of that 
object in meters. Some objects may lie between two powers of 10. 

When you are done placing all of the cards, record your results in the table on the next page and answer 
the questions that follow. 

Card choices adapted from Tretter, T. R., Jones, M. C, Andre, T., Negishi, A., & Minogue, J. (2005). Con- 
ceptual Boundaries and Distances: Students' and Experts' Concepts of the Scale of Scientific Phenomena. 
Journal of Research in Science Teaching. 

Table 1.11: 

Size (meters) Objects 

10° 21. height of a typical NBA basketball player 

4. height of a typical 5-year-old child 

10 _1 20. length of a phone book 

16. length of a business envelope 
9. width of an electrical outlet cover 



47 www.ckl2.org 



Table 1.11: (continued) 



Size (meters) 



Objects 



10" 



10" 



10" 



10~ 5 
10~ 6 

io- 7 



17. diameter of a quarter 

7. width of a typical wedding ring 

14. length of an apple seed 

I. thickness of a penny 

23. thickness of a staple 

II. thickness of sewing thread 

6. length of a dust mite 

8. length of an amoeba 

18. length of a human muscle cell 

3. diameter of a red blood cell 
13. width of a bacterium 

24. wavelength of visible light (between 10~ 7 

io- 6 ) 

15. diameter of a virus 



and 



io- 



io- 9 

io- 10 

io- 15 



10. diameter of a ribosome 

5. width of a proteinase enzyme 

19. diameter of a carbon nanotube 

12. width of a water molecule 
22. diameter of a nitrogen atom 
2. nucleus of an oxygen atom 



Questions 

1. Which items were the hardest for you to estimate size for? Why? 

Students will probably list small objects they know the least about. For example, if they haven't taken 
biology, they may list virus, ribosome, etc. 

2. Why are we using powers of 10 for the number line instead of a regular linear scale (like a meter stick)? 

With a powers of 10 scale, we can spread the unit markers out evenly so that we can clearly place and see 
all of the cards. If we used a linear scale, most of the cards would pile up on top of each other. And we 
can't easily make marks much smaller than a millimeter anyway, so we couldn't make or see our scale if it 
were linear! 

Cutting it Down Activity: Teacher Instructions & Key 

Purpose 

The purpose of this activity is to help students understand the smallness of the nanoscale, appreciate the 
impossibility of creating nanoscale materials with macro scale objects, and to understand the invisibility 
of the nanoscale to the unaided eye. [1] 

Materials 



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48 



For each group of students, provide 

• Scissors 

• A strip of paper (cut a narrow strip from an 8.5 X 11 inch sheet of paper, approximately 8.5 inches 
long by 1/4 inch wide, or 216 mm X 5 mm) 

• Pen or pencil 

• Ruler 

• Calculator 

Classroom Activity 

Show the students the strip of paper and tell them what its dimensions are. Explain to them that the 
challenge is to cut the piece of paper in half repeatedly in order to make it 10 nm long. 

Have the students get in pairs and give each pair the ruler, calculator, scissors, pen/pencil (if necessary), 
strip of paper, and the Cutting It Down Activity: Student Worksheet. Remind them to answer the first 
two questions on the worksheet before they begin cutting. Tell them they have 10 minutes to complete the 
activity. 

As a variation, you could have students do the exercise more than once with different kinds of scissors or 
other cutting tools to demonstrate the power and limitations of tools. 

Discussion 

When the students have finished the activity, discuss the questions on their worksheets. Focus on the 
following questions first: 

• Were their predictions to the first two questions accurate? 

• How many times were they able to cut the paper? 

After discussing these questions, focus on the remaining questions on their worksheets. As a closing point, 
emphasize that the demonstration shows how small nano really is and how inadequate macro scale tools 
(like the scissors), are in dealing with the nanoscale. 

• If you have had students use different kinds of scissors or other cutting tools, you can also discuss 
the relationship between form and size of the tool and its precisions and usefulness at a certain size 
scale. For example, an x-acto blade can be used to make much finer cuts than a pair of scissors, 
although both are too big to be useful at the nanoscale. 

[1] Adaped from http://mrsec.wisc.edu/Edetc/IPSE04/educators/activities/cuttingNano.html 

Student Instructions 

How many times do you think you would need to cut a strip of paper in half in order to make it between 
zero and 10 nanometers long? In this activity, you'll cut a strip of paper in half as many times as you can, 
and think about the process. 

BEFORE you begin cutting the strip of paper, answer the following questions (take a guess): 

1. How many times do you need to cut the paper in half to obtain a 10 nanometer long piece? 
Answers will vary, since this is a prediction. Should be a fairly large integer value. 

2. How many times do you think you can cut the paper before it becomes impossible to cut? 

Answers will vary, since this is a prediction. Should be an integer value that is smaller than the answer to 
question 1. 

49 www.ckl2.org 



Now cut the strip of paper in half as many times as you can. Remember to keep track of how many cuts 
you make. 

AFTER completing the activity, answer the following questions. 

3. Were your predictions to the above two questions accurate? 

Answers will vary, but should indicate if their predictions matched their results. 

4. How many times were you able to cut the paper? 

Answers will vary, but should be an integer number, likely in the range of 6 - 8 cuts. 

5. How close was your smallest piece to the nanoscale? 

Very far. By cutting with a typical pair of scissors, you probably can get down to about the 1 mm range, 
which is 10~ 3 meters. The nanoscale range is 1CT 7 to 10~ 9 meters, or 4 to 6 powers of ten smaller. 

6. Why did you have to stop cutting? 

Couldn't position the paper on the scissors; the scissors were too big relative to the paper to cut any more, 
etc. 

7. Can macroscale objects, like scissors, be used at the nanoscale? 
No. 

8. Can you think of a way to cut the paper any smaller? 

Answers might include using a microscope, smaller scissors, or finer cutting tools. 

Activity: Teacher Key 

In this activity, you will explore your perceptions different sizes. For each of the following items, indicate 
its size by placing an "X" the box that is closest to your guess. 

Key: 

A. Less than 1 nanometer (1 nm) [Less than 10~ 9 meter] 

B. Between 1 nanometer (nm) and 100 nanometers (100 nm) [Between 10~ 9 and 10 -7 meters] 

C. Between 100 nanometers (100 nm) and 1 micrometer (1 //m) [Between 10 and 10 -6 meters] 

D. Between 1 micrometer (1 /urn.) and 1 millimeter (1 mm) [Between 10~ 6 and 10~ 3 meters] 

E. Between 1 millimeter (1 mm) and 1 centimeter (1 cm) [Between 10~ 3 and 10~ 2 meters] 

F. Between 1 centimeter (1 cm) and 1 meter ( m) [Between 10 -2 and 10° meters] 

G. Between 1 meter and 10 meters [Between 10° and 10 1 meters] 
H. More than 10 meters [More than 10 1 meters] 

Table 1.12: 



Less 


1 nm to 


100 nm 


1 //Hi to 


1 mm to 


1 cm to 


1 m 


to 


More 


than 


100 nm 


to 1 /urn 


1 mm 


1 cm 


1 m 


10 m 




than 


1 nm 
















10 m 



Object ABCDEFGH 

1. Width x 

of a hu- 
man hair 

www.ckl2.org 50 



Table 1.12: (continued) 



Less 


1 nm to 


100 nm 


1 jum to 


1 mm to 


1 cm to 


1 m 


to 


More 


than 


100 nm 


to 1 fxm 


1 mm 


1 cm 


1 m 


10 m 




than 


1 nm 
















10 m 



2. 

Length 
of a 

football 
field 

3. Diam- 
eter of a 
virus 

4. Di- 
ameter 
of a hol- 
low ball 
made 

of 60 
carbon 
atoms (a 
"bucky- 
ball") 

5. Diam- 
eter of a 
molecule 
of 
hemoglobin 

6. Di- x 
ameter of 

a hydro- 
gen atom 
7. 

Length 
of a 

molecule 
of su- 
crose 
8. Diam- 
eter of a 
human 
blood 
cell 
9. 

Length 
of an ant 
10. 

Height 
of an 

elephant 



51 



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Table 1.12: (continued) 



Less 


1 nm to 


100 nm 


1 jum to 


1 mm to 


1 cm to 


1 m 


to 


More 


than 


100 nm 


to 1 fxm 


1 mm 


1 cm 


1 m 


10 m 




than 


1 nm 
















10 m 



11. Di- 
ameter 
of a 

ribosome 
12. 

Wave- 
length of 
visible 
light 
13. 

Height of 
a typical 
adult 
person 
14. 

Length 
of a new 
pencil 
15. 

Length 
of a 

school 
bus 

16. Di- 
ameter 
of the 
nucleus 
of a 

carbon 
atom 
17. 

Length 
of a grain 
of white 
rice 
18. 

Length 
of a 

postage 
stamp 



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52 



Table 1.12: (continued) 



Less 


1 nm to 


100 nm 


1 jum to 


1 mm to 


1 cm to 


1 m 


to 


More 


than 


100 nm 


to 1 fxm 


1 mm 


1 cm 


1 m 


10 m 




than 


1 nm 
















10 m 



19. 

Length 

of a 

typical 

science 

textbook 

20. 

Length 

of an 

adult's 

little 

finger 



Adapted from Tretter, T. R., Jones, M. G., Andre, T., Negishi, A., & Minogue, J. (2005). Conceptual 
Boundaries and Distances: Students' and Experts' Concepts of the Scale of Scientific Phenomena. Journal 
of Research in Science Teaching. 

Scale of Small Objects: Teacher Key 

1. Indicate the size of each object below by placing an "X" the appropriate box. 
Key: 

A. Less than 1 nanometer (1 nm) [Less than 10~ 9 meter] 

B. Between 1 nanometer ( nm) and 100 nanometers (100 nm) [Between 10~ 9 and 10~ 7 meters] 

C. Between 100 nanometers (100 nm) and 1 micrometer (1 //m) [Between 10 and 10 -6 meters] 

D. Between 1 micrometer (1 /urn.) and 1 millimeter (1 mm) [Between 10~ 6 and 10~ 3 meters] 

E. Between 1 millimeter (1 mm) and 1 centimeter (1 cm) [Between 10~ 3 and 10~ 2 meters] 

Table 1.13: 



Less than 1 nm 



1 nm 

100 nm 



to 100 nm to 1 //m ljum to 1 mm 1 mm to 1 cm 



Object 

1. Width of a 
human hair 

2. Diameter 
of a hollow ball 
made of 60 car- 
bon atoms (a 
"buckyball") 

3. Diameter 
of a hydrogen 
atom 



B 



D 

x 



E 



53 



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Table 1.13: (continued) 



Less than 1 nm 1 nm to 100 nm to 1 //m ljum to 1 mm 

100 nm 



1 mm to 1 cm 



4. Diameter of 
a human blood 
cell 

5. Wavelength 
of visible light 



2. Order the following items in order of their size, from smallest to largest. 

a. Width of a water molecule 

b. Diameter of a gold atom 

c. Thickness of a staple 

d. Diameter of a virus 

e. Length of an amoeba 

f. Diameter of a carbon nanotube 
Smallest: 



_d_ 
_a_ 

f 



_d_ 

c 



Largest: 



Unique Properties at the Nanoscale 
Teacher Lesson Plan 

Contents 

• Unique Properties at the Nanoscale: Teacher Lesson Plan 

• Unique Properties at the Nanoscale: PowerPoint with Teacher Notes 

• Unique Properties Lab Activities: Teacher Instructions 

• Unique Properties at the Nanoscale: Teacher Reading 

• Unique Properties at the Nanoscale Quiz: Teacher Key 



Orientation 

This lesson is central to understanding the science that occurs at the nanoscale, and contains the most 
rigorous science content. 



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54 



• The Unique Properties at the Nanoscale PowerPoint focuses on how and why properties of materials 
change at the nanoscale. 

• The Student Reading on Size-Dependent Properties provides more details on why properties change 
at the nanoscale. It may be appropriate for students taking college preparatory chemistry. 

• The Unique Properties Lab Activities demonstrate specific aspects of size-dependent properties with- 
out using nanoparticles. It is appropriate for most students. 

• The Unique Properties Quiz tests students understanding of size-dependent properties. 

Essential Questions (EQ) 

What essential questions will guide this unit and focus teaching and learning? 

(Numbers correspond to learning goals overview document) 

2. Why are properties of nanoscale objects sometimes different than those of the same materials at the 
bulk scale? 

5. Why do our scientific models change over time? 

Enduring Understandings (EU) 

Students will understand: (Numbers correspond to learning goals overview document) 

2. There are enormous scale differences in our universe, and at different scales, different forces dominate 
and different models better explain phenomena. 

3. Nanosized particles of any given substance exhibit different properties than larger particles of the same 
substance. 

Key Knowledge and Skills (KKS) 

Students will be able to: (Numbers correspond to learning goals overview document) 

2. Explain why properties of nanoscale objects sometimes differ from those of the same materials at the 
bulk scale. 

Prerequisite Knowledge and Skills 

• Familiarity with properties of matter. 

• Some knowledge of atomic structure, Bohr's model of the atoms and the quantum mechanical model 
of the atom. 

• Familiarity with polarity of molecules. 

Related Standards 

. NSES Science and Technology: 12EST2.1, 12EST2.2 

. NSES Science as Inquiry: 12ASI2.3 

. AAAS Benchmarks: 11D Scale #1, 11D Scale #2 

Table 1.14: 

Day Activity Time Materials 

Prior to this lesson Homework: Reading: 45 min Photocopies of Size- 

Size- Dependent Proper- Dependent Properties: 

ties Student Reading 

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Table 1.14: (continued) 



Day 



Activity 



Time 



Materials 



Day 1 (50 min) 



Show the PowerPoint 
slides: Unique Proper- 
ties at the Nanoscale, 
using teacher's notes as 
talking points. Discuss: 

• Normal properties 
of a substance. 

• What properties 
change from bulk 
characteristics to 
nanoscale proper- 
ties, and how they 
change* 

• How the domi- 
nance of electro- 
magnetic forces 
make a difference 
in properties* 

• How the quantum 
mechanical model 
of the atom, 
uncertainty of 
measurement, and 
tunneling make 
a difference for 
nanoscale objects* 

* Note: Not required by 
NSES Standards 



40 min 



PowerPoint slides: 

Unique Properties at 
the Nanoscale 
Computer and Projec- 
tor 



Prepare for the Unique 
Properties Station Lab 
Review student group- 
ing and procedural ar- 
rangements 



10 min 



Photocopies of Student 
Lab Worksheet 



Day 2 (40 min) 



Conduct Unique Prop- 
erties Lab Activity 



40 min 



Post Student Directions 
at each station and 
prepare stations per 
Teacher Lab Instruc- 
tions 



Homework: Complete 30 min 
the Student Lab Work- 
sheet 



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56 



Table 1.14: (continued) 



Day Activity Time Materials 

Day 3 (45 min) (op- Discuss student results 30 min 
tional) from the lab activity, 

and review concepts of 

unique properties at the 

nanoscale 

Quiz: Unique Proper- 15 min Photocopies of Unique 

ties at the Nanoscale Properties at the 

Nanoscale: Student 

Quiz 

Teacher Key for correct- 
ing Student Quiz 



Unique Properties at the Nanoscale 




The science behind nanotechnology 
Are You a Nanobit Curious? 

• What's interesting about the nanoscale? 

— Nanosized particles exhibit different properties than larger particles of the same substance 

• As we study phenomena at this scale we... 

— Learn more about the nature of matter 

— Develop new theories 

— Discover new questions and answers in many areas, including health care, energy, and technology 

— Figure out how to make new products and technologies that can improve people's lives 

Size-Dependent Properties 

How do properties change at the nanoscale? 
Properties of a Material 

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Figure 1.13 

• A property describes how a material acts under certain conditions 

• Types of properties 

— Optical (e.g. color, transparency) 

— Electrical (e.g. conductivity) 

— Physical (e.g. hardness, melting point) 

— Chemical (e.g. reactivity, reaction rates) 

• Properties are usually measured by looking at large (~ 10 23 ) aggregations of atoms or molecules 
Optical Properties Example: Gold 

• Bulk gold appears yellow in color 

• Nanosized gold appears red in color 

— The particles are so small that electrons are not free to move about as in bulk gold 

— Because this movement is restricted, the particles react differently with light 

Optical Plroperties Example: Zinc Oxide [ZnO) 

• Large ZnO particles 

— Block UV light 

— Scatter visible light 

— Appear white 

• Nanosized ZnO particles 



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58 



V 




'Bulk" gold looks yellow 



12 nanometer gold "Bulk" gold 
looks yellow particles look red 



Figure 1.14 

— Block UV light 

— So small compared to the wavelength of visible light that they don't scatter it 

— Appear clear 

Electrical Properties Example: Conductivity of Nanotubes 

• Nanotubes are long, thin cylinders of carbon 

— They are 100 times stronger than steel, very flexible, and have unique electrical properties 

• Their electrical properties change with diameter, "twist", and number of walls 

— They can be either conducting or semi-conducting in their electrical behavior 

Physical Properties Change: Melting Point of a Substance 

• Melting Point (Microscopic Definition) 

— Temperature at which the atoms, ions, or molecules in a substance have enough energy to 
overcome the intermolecular forces that hold the them in a "fixed" position in a solid 

— Surface atoms require less energy to move because they are in contact with fewer atoms of the 
substance 

Table 1.15: Physical Properties Example: Melting Point of a Substance II 



At the macroscale 



At the nanoscale 



The majority of the atoms are almost all on the inside of the ...split between the inside and the 

object surface of the object 





Changing an object's size... 



The melting point... 



...has a very small effect on the ...has a big effect on the percent- 
percentage of atoms on the sur- age of atoms on the surface 
face 
...doesn't depend on size ...is lower for smaller particles 



59 



Size-Dependant Properties 

Why do properties change? 



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"Traditional" ZnO 
sunscreen is white 





Nanoscale ZnO 
sunscreen is clear 



Zinc oxide nanoparticles 

Figure 1.15 



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60 




Multi-walled 



Electric current 
varies by tube 
structure 




Zlg zag 



Armchair 



Ch.ial 



Figure 1.16 





In contact with 3 atoms 
In contact with 7 atoms 



Figure 1.17 



61 



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• There are enormous scale differences in our universe! 

• At different scales 

— Different forces dominate 

— Different models better explain phenomena 

• (See the Scale Diagram handout) 
Scale Changes Everything II 

• Four important ways in which nanoscale materials may differ from macroscale materials 

— Gravitational forces become negligible and electromagnetic forces dominate 

— Quantum mechanics is the model used to describe motion and energy instead of the classical 
mechanics model 

— Greater surface area to volume ratios 

— Random molecular motion becomes more important 

Dominance of Electromagnetic Forces 

• Because the mass of nanoscale objects is so small, gravity becomes negligible 

— Gravitational force is a function of mass and distance and is weak between (low-mass) nanosized 
particles 



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62 




-:-■ 



Figure 1.18 



63 



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Electromagnetic force is a function of charge and distance is not affected by mass, so it can be 

very strong even when we have nanosized particles 

The electromagnetic force between two protons is 10 36 times stronger than the gravitational 

force! 



Quantum Effects 




V 



Macrogold 



NanogoW 




Figure 1.19 

• Classical mechanical models that we use to understand matter at the macroscale break down for... 

— The very small (nanoscale) 

— The very fast (near the speed of light) 

• Quantum mechanics better describes phenomena that classical physics cannot, like... 

— The colors of nanogold 

— The probability (instead of certainty) of where an electron will be found 

Surface Area to Volume Ratio Increases 

• As surface area to volume ratio increases 

— A greater amount of a substance comes in contact with surrounding material 

— This results in better catalysts, since a greater proportion of the material is exposed for potential 
reaction 



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64 




^ 



7— 











'**1n ? -lm l AitM- % ■ rW»^«*- Wf» y 









c 








/ 









A«. • « * (Ijii' x //• » m 2 



Figure 1.20 



Random Molecular Motion is Significant 



• 



i 



:- 



■ 



i 



Figure 1.21 



Tiny particles (like dust) move about randomly 

— At the macroscale, we barely see movement, or why it moves 

— At the nanoscale, the particle is moving wildly, batted about by smaller particles 

Analogy 



65 



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— Imagine a huge (10 meter) balloon being batted about by the crowd in a stadium. From an 
airplane, you barely see movement or people hitting it; close up you see the balloon moving 
wildly. 

What Does This All Mean? 

• The following factors are key for understanding nanoscale-related properties 

— Dominance of electromagnetic forces 

— Importance of quantum mechanical models 

— Higher surface area to volume ratio 

— Random (Brownian) motion 

• It is important to understand these four factors when researching new materials and properties 

Teacher Notes 

Overview 

This series of slides introduces and describes some of the differences in properties between nanoscale and 
macroscale (bulk) materials and the underlying causes of these differences. 

Slide 1: Unique Properties at the Nanoscale 

Explain that with the new scientific tools that operate on the nanoscale, we are finding out that many 
familiar materials act differently and have different characteristics and properties when we have very small 
(nanoscale) quantities of them. This presentation will discuss these size-dependent properties and why 
they change at the nanoscale. 

Slide 2: Are You a Nanobit Curious? 

This slide focuses on the differences in properties between nanoscale and macroscale materials. It is impor- 
tant to emphasize that not all nanoscale materials will exhibit different properties from their macroscale 
counterparts. The differences in properties depend on many things besides size, including arrangement of 
atoms and/or molecules in the particles, charge, and shape. 

This slide also highlights why we should care about nanoscience: It will change our lives and change our 
understanding of matter. We are continually learning more and more about the properties of nanoscale 
particles, including how to manipulate them to suit our needs. 

Slide 3: Size-Dependent Properties 

The next few slides focus on how nanosized materials exhibit some size-dependent effects that are not 
observed in bulk materials. 

Slide 4: Properties of a Material 

This slide summarizes the content in the "What Does it Mean to Talk About the Characteristics and 
Properties of a Substance?" and "How Do We Know the Characteristics and Properties of Substances?" 
paragraphs in the student reading on sizedependent properties. It is important to talk with your students 
about how we know about the properties of materials — how are they measured and on what sized particles 
are the measurements made? In most cases, measurements are made on macroscale particles, so we tend 
to have good information on bulk properties of materials but not the properties of nanoscale materials 
(which may be different). 

This slide also points out four types of properties that are often affected by size. This is not an exhaustive 
list but rather a list of important properties that usually come up when talking about nanoscience. 

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Slide 5: Optical Properties Example: Gold 

The gold example is discussed in the reading and is included here to give a simple comparison between 
the nano and bulk properties of a particular material. This slide aligns with the "What's Different at the 
Nanoscale" paragraph in the properties reading. It is important to point out to your students that we 
can't say exactly what color a material will always be at a given particle size. This is because there are 
other factors involved like arrangement of atoms and molecules in the particles and charge(s) present on 
particles. However, it is possible to control for these various factors to create desired effects, as in this case 
the creation of "red" gold using 12 nanometer-sized particles. 

Slide 6: Optical Properties Example: Zinc Oxide [ZnO) 

This slide highlights another properties example that is in the reading. Here a comparison is made between 
large and nanosized zinc oxide particles — particles typically found in sunscreen. This is a good slide to 
use to discuss the electromagnetic spectrum, where ultraviolet rays are on the spectrum, and why we are 
so concerned about them. It can also be used to spark discussion about visible light and how it interacts 
with matter to allow us to see objects as having different colors and opacities. More detail on this topic is 
provided in the Nanosense Clear Sunscreen unit. 

Slide 7: Electrical Properties Example: Conductivity of Nanotubes 

This slide highlights another properties example that is not in the reading. Electrical properties of materials 
are based on the movement of electrons and the spaces, or "holes," they leave behind. The electronic 
properties of a nanotube depend on the direction in which the sheet was rolled up. Some nanotubes are 
metals with high electrical conductivity, while others are semiconductors with relatively large band gaps. 
Which one it becomes depends on way that it is rolled (also called the "chirality" of the nanotube"). If 
it's rolled so that its hexagons line up straight along the tube's axis, the nanotube acts as a metal. If it's 
rolled on the diagonal, so the hexagons spiral along the axis, it acts as a semiconductor. See the "Unique 
Properties at the Nanoscale: Teacher Reading" for more information. 

Slide 8: Physical Properties Change: Melting Point of a Substance 

Note that even in a solid, the atoms are not really "fixed" in place but vibrating around a fixed point. In 
liquids, the atoms also rotate and move past each other in space (translational motion) though they don't 
have enough energy to completely overcome the intermolecular forces and move apart as in a gas. 

Slide 9: Physical Properties Example: Melting Point of a Substance II 

At the nanoscale, a smaller object will have a significantly greater percentage of its atoms on the surface 
of the object. Since surface atoms need less energy to move (because they are in contact with fewer atoms 
of the substance), the total energy needed to overcome the intermolecular forces hold them "fixed" is less 
and thus the melting point is lower. 

Slide 10: Size-Dependant Properties 

The next few slides focus on why nanosized materials exhibit size-dependent effects that are not observed 
in bulk materials. 

Slide 11: Scale Changes Everything 

Ask your students to refer to the Scale Diagram handout. Use the diagram to point out how there are 
enormous scale differences in the universe (left part of the diagram), and where different forces dominate 
and different models better explain phenomena (right part of diagram). Scale differences are also explored 
in more detail in "Visualizing the Nanoscale: Student Reading" from lesson 2. 

Slide 12: Scale Changes Everything II 

This slide highlights four ways in which nanoscale materials may differ from their macroscale counterparts. 
It is important to emphasize that just because you have a small group of some type of particle, it does 

67 www.ckl2.org 



not necessarily mean that a whole new set of properties will arise. Whether or not different observable 
properties arise depends not only on aggregation, but also on the arrangement of the particles, how they 
are bonded together, etc. This slide sets up the next four slides, where each of the four points (gravity, 
quantum mechanics, surface area to volume ratio, random motion) is described in more detail. 

Slide 13: Dominance of Electromagnetic Forces 

This slide compares the relative strength between the electromagnetic and gravitational forces. The grav- 
itational force between two electrons is feeble compared to the electromagnetic forces. The reason that 
you feel the force of gravity, even though it is so weak, is that every atom in the Earth is attracting 
every one of your atoms and there are a lot of atoms in both you and the Earth. The reason you aren't 
bounced around by electromagnetic forces is that you have almost the same number of positive charges as 
negative ones, so you are (essentially) electrically neutral. Gravity is only (as far as we know) attractive. 
Electromagnetic forces (which include electrical and magnetic forces) can be either attractive or repul- 
sive. Attractive and repulsive forces cancel each other out; they neutralize each other. Since gravity has 
no repulsive force, there's no weakening by neutralization. So even though gravity is much weaker than 
electrical force, gravitational forces always add to each other; they never cancel out. 

Slide 14: Quantum Effects 

This slide highlights why, at the nanoscale, we need to use quantum mechanics to describe behavior rather 
than classical mechanics. The properties reading describes the differences. You can decide how much 
discussion to have about classical and quantum mechanics with your students. For the purposes of this 
introductory unit, it is important to let students know that we use a different set of "rules" to describe 
particles that fall into the nanoscale and smaller range. 

Slide 15: Surface Area to Volume Ratio Increases 

This slide highlights the fact that as you decrease particle size, the amount of surface area increases. The 
three-part graphic on the slide illustrates how, for the same volume, you can increase surface area simply 
by cutting. Each of the three blocks has the same total volume, but the block that has the most cuts has 
a far greater amount of surfaces area. This is an important concept since it effects how well a material 
can interact with other things around it. With your students, you can use following example. Which will 
cool a glass of water faster: Two ice cubes, or the same two ice cubes (same volume of ice) that have been 
crushed? 

Slide 16: Random Molecular Motion is Significant 

This slide highlights the importance of random ("Brownian") motion at small scales. Tiny particles, such 
as dust, are in a constant state of motion when seen through microscope because they are being batted 
about by collisions with small molecules. These small molecules are in constant random motion due to 
their kinetic energy, and they bounce the larger particle around. At the macroscale, random motion is 
much smaller than the size of the particle, but at the nanoscale this motion is large when compared to the 
size of the particle. 

A nice animation that illustrates this concept is available at http: //galileo. phys.virginia.edu/classes/ 
109N/more_stuf f /Applets/brownian/brownian . html 

Slide 17: What Does This All Mean? 

This slide summarizes the key ideas in the properties reading: Understanding how electromagnetic forces, 
quantum models, surface area to volume ratio, and random motion influence properties of nanoscale ma- 
terials helps us to better understand how to create materials with specific properties. 



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Lab Activities: Teacher Instructions 

Overview 

There are three sets of curricular materials for this lab: 

1. Unique Properties Lab Activities: Teacher Instructions. This document, which includes the 
purpose, safety precautions, and procedures for each lab station, and a complete list of materials for 
station. Occasionally, a suggestion is given for optional variations on the labs, under the heading 
"Teacher Notes." 

2. Unique Properties Lab Activities: Student Instructions. The set of directions for students 
is to be printed and posted at each of the appropriate lab stations. They include a statement of 
purpose, safety precautions, materials needed and procedures for the student to follow. 

3. Unique Properties Lab Activities: Student Worksheet. Each student should be given this 
worksheet onto which they will record their observations. The worksheet also includes questions 
about each lab, designed to stimulate the student to think about how the lab demonstrates concepts 
fundamental to the mechanisms that make nanotechnology unique. 

Each of the following labs is designed to demonstrate a specified aspect of nanotechnology without actually 
using nanoparticles. The lab is to be set up at multiple stations. Each student or group of students will 
conduct investigations at each station. You may choose to vary the way that students are assigned to lab 
stations without compromising the learning experience for the students, as long as they have an opportunity 
to share their thoughts and observations with each other. Note that Lab stations D through H are all on 
surface area to volume effects. 

Post the appropriate Student Instructions at each station for students to follow. There needs 
to be running tap water and paper towels at each lab station. The instructions for each lab will specify if 
goggles are needed, as well as any other safety precautions. Each student should have their own lab sheet 
for recording their data and answering questions. 

The lab stations are: 

Serial Dilution Lab 

Ferrofluid Display Cell Lab 

Bubbles Self-Assembly Lab 

Surface Area to Volume Effects... Which Shape Can Dissolve the Fastest? 

More Surface Effects... Faster Explosion? 

More Surface Effects... Is All Water the Same? 

Surface Area to Volume Effects... Burn Baby Burn! 

Surface Area to Volume Effects... Bet I Can Beat'cha! 

A complete list of materials can be found on the last page of this set of teacher instructions. 

Time Duration 

Each lab should take approximately 8 minutes or less. It should take students no more than 50 minutes 
to complete all of the lab activities. Lab Stations D through G illustrate the concept of surface area to 
volume ratio effects, so if time is short, you may want to make some of those lab stations optional, use 
only a subset of these labs, or assign different stations to different groups of students. 

Lab Station A 

Serial Dilution Lab 

Purpose 

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The purpose of this lab is to investigate the effects of decreasing the concentration of a solution on the 
two properties of color and odor. Nanosized materials, (from 1 to 100 nm), often appear to have different 
colors and scents than they do at larger sizes. 

Safety Precautions 

• Wear goggles while conducting this lab. 

• Do not eat or drink anything while in the lab. 

Materials 

Reagents 

A stock solution "assigned" the value of 1.0 Molar. You can use unsweetened, scented Kool-Aid to make the 
solution. Prepare as directed on the package, and then dilute with twice as much water as the directions 
indicate. Alternately, you may use 1 drop of food coloring per liter of water, and add an ester of your 
choice to this mixture. You may have to experiment to ensure that with a 5-part serial dilution, the odor 
and color change enough from one test tube to another for students to notice. 

Materials 

• A 1.0 M colored stock solution 

• Five test tubes that can hold 10 - mL each 

• One 25 - mL graduated cylinder 

• A test tube holder 

• Grease marker 

• Tap water 

• One 1.0 — mL graduated pipette, plastic or glass 

• A sheet of white paper for background, to help students to judge color 

Procedures 
Concentration 

1. Label each of your test tubes from 1 to 5. 

2. Use a pipette to place 10.0 mL of 1.0 Molar of colored solution into test tube #1. 

3. Remove 1.0 mL from test tube #1 and inject this into test tube #2. Then add 9.0 mL of water into 
test tube #2. 

4. Remove 1.0 mL from test tube #2 and inject this into test tube #3. Then add 9.0 mL of water into 
test tube #3. 

5. Continue in this fashion until you have completed test tube #5. 

6. Note that each subsequent test tube has the concentration of the previous test tube divided by 10. 

7. On your lab sheet, record the concentration of the solution in each test tube. 

Color 

1. Hold the white paper behind your test tubes to determine the color change. 

2. Use test tube #1 as the strongest color. 

3. Continue from test tube #2 to #5 using the gauge below. 

12 3 4 5 

full strength of ► no visible color 

solution A increasing lighter color 

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4. Record on your lab sheet the strength of each test tube according to the scale above. At what 
strength are you no longer able to detect color? Explain why this has happened. 

Odor 




1. Waft, with your hand, the air over the top of the test tube towards your nose. Sniff. Record the strength 
of odor according to the scale below on you lab worksheet. 

2. Use test tube #1 as the strongest odor. 

3. Continue with test tube #2 to #5 in the same manner. 



Oder in test 
tube #1 



■+ no odor 



decreasing strength of odor 

4. Record on your lab sheet the concentration at which the odor of your solution is no longer detectable. 
Record other observations and questions as asked on the lab sheet. Explain why you think this happened. 

Teacher Notes 

If you have a spect-20 spectrophotometer available, you may use this to measure the absorption of each of 
the five solutions. 

Lab Station B 

Ferrofluid Display Cell Lab 

Purpose 

The purpose of this lab is to design a series of activities that investigate and compare the force of magnetism 
in ferrofluid (small pieces of iron suspended in fluid) and in a solid piece of iron. 



71 



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Safety Precautions 

• Do not shake or open the bottle of ferrofluid! 

• Use care when handling glass. 

Materials 

• One capped bottle of ferrofluid (nanosized iron particles suspended in a solution). A Ferrofluid Pre- 
form Display Cell can be obtained for $30 plus tax and shipping from: http : //www . teachersource . 
com/catalog/ (Search for item "FF-200") 

• A plastic 100 mL -graduated cylinder 

• A large empty test tube and stopper 

• A piece of iron (a slug or rod), about 1 - inch in length. This can be purchased from a chemical 
supply house. You may replace a slug of iron with an iron nail or washer, available from a hardware 
store. Note: Most nails are steel rather than iron. 

• Two circle magnets. These magnets come with the ferrofluid display cell. You may add other magnets 
to provide variety for students. 

Procedures 

1. Make observations and record your observations of the ferrofluid and the iron object separately. 

2. Predict how the magnet will influence the ferrofluid and the iron object. 

3. Use the magnets to observe how the force of magnetism influences the ferrofluid and the iron object. 

4. Record on your lab sheet your conclusions in the designated place on your lab sheet. 

Teacher Notes 

You may also check out other ferrofluid products if you are interested. There is an entire kit designed for 
a variety of experiments using ferrofluid and an experiment booklet you can purchase separately. 

Lab Station C 

Bubbles Self-Assembly Lab 

Purpose 

One of the methods proposed to mass manufacture nanosized objects is to use nature's own natural tendency 
to self-assemble objects. Fluid or flexible objects will automatically fill the space of the container, taking 
the most efficient shape. The purpose of this lab is to demonstrate how bubbles self-assemble. 

Safety Precautions 

• Do not eat or drink anything in lab. 

• Use caution when handling glassware. 

Materials 

• A bubble solution [Bubble Formula: Dawn Ultra or Joy Ultra/ Water (Distilled Water Works 
Best) /Glycerine or White Karo Syrup (Optional) 1 Part/10 Parts/. 25 Parts] 

• Small shallow dish 

• Toothpicks 

• Paper towels 

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• Straw (coffee stirrers work best) 
Procedures 

1. Stir the solution with the straw to create bubbles, as needed. 

2. Pour about 10.0 niL of bubble solution into the shallow dish. 

3. Caution: Be careful not to spill the solution or to drop the dish! 

4. Draw what you see in your worksheet. This is your "before" diagram. 

5. Take the toothpick and pop one of the bubbles. Notice how the arrangement of bubbles changed. 
Draw what has happened. This is your "after" diagram. Repeat this procedure several times (you 
do not need to illustrate after the first "before" and "after" observations). 

Lab Stations D through G 

Surface Area to Volume Effects 

Overview 

One of the characteristics of nanosized objects is that the surface area to volume ratio is much greater than 
bulk sized objects. The purpose of lab investigations D through H is to offer a variety of opportunities for 
students to compare the effects of varying the surface area to volume ratio on the rate of dissolving (Lab 
D), the rate of bubble formation (Lab E), the time required to boil the same amount of water (Lab F) and 
the rate of burning (Lab G). 

Lab Station D 

Surface Area to Volume Effects... Which Shape Can Dissolve the Fastest? 

Purpose 

One of the characteristics of nanosized objects is that the surface area to volume ratio is much greater than 
bulk sized objects. The purpose of this lab investigation is to compare the effects of varying the surface 
area to the volume ratio for two samples of the same substance and mass, but different particle size, on 
the rate of dissolving in water. 

Safety Precautions 

• Do not eat or drink anything in lab. 

• Use caution when handling glassware. 

• Wear safety goggles. 

Materials 

• Two sugar cubes per group 

• Granulated sugar, about a cup per class 

• A digital balance or scale, with readout to 0.1 gram. A standard laboratory balance can be used 
instead. 

• Two 250 - mL Erlenmeyer flasks 

• A 100 - mL graduated cylinder 

• A grease marker 

• Tap water, about 50 - mL 

• A clock or watch with a second hand 

Procedures 

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1. Using a grease marker, label one Erlenmeyer flask #1 and the other :2. (These may have already 
been marked. No need to mark twice.) 

2. Set the scale to zero, after placing a square of paper on top of the scale (this is called "taring"). 

3. Measure and record the mass of two cubes of sugar. Put the sugar cubes into flask #1. 

4. Measure and record a mass of granulated sugar equal to the mass of the two sugar cubes. 

5. Put the granulated sugar into flask #2. 

6. Using your graduated cylinder, add 100.0 mL of tap water to each flask. 

7. Gently swirl each flask exactly 60 seconds. 

8. Record the relative amount of sugar that has dissolved in each flask on your lab sheet. 

9. Swirl each flask for another 60 seconds. 

10. Record the relative amount of sugar that has dissolved in each flask on your lab sheet. Answer the 
questions asked about the rates of dissolving. 

Teacher Notes 

You may vary this lab by: 

• Using salt rather than sugar. Salt comes in chunky crystals in rock salt and regular granulated salt. 

• Varying the types of sugar to also include superfine and/or powdered sugar. 

If you use any additional substances or variations in concentration, you will have to adjust the directions 
and the materials needed accordingly. 

Lab Station E 

More Surface Effects... Faster Explosion? 

Purpose 

The purpose of the following activities is to give you more experience with examining the effects of changing 
surface area to volume ratios. Faster explosion looks at the effect of different surface area to volume 
ratios on the speed of reaction. 

Safety Precautions 

• Do not eat or drink anything in the lab. 
Materials 

• Two empty film canisters and their lids (clear canisters work better than black) 

• One tablet of Alka Seltzer® per group 

• One small mortar and pestle 

• Clock or watch with a second hand 

Procedures 

1. Break the Alka Seltzer® tablet in half as exactly as you can. 

2. Put one of the halves of the Alka Seltzer® tablet into the mortar and crush it with the pestle until 
it is finely granulated. 

3. Place the uncrushed Alka Seltzer® and the crushed Alka Seltzer® each into a different film canister. 
Each canister should contain Alka Seltzer® before you proceed to the next step. 

4. Simultaneously fill each film canister halfway with tap water. Quickly put their lids on. 

www.ckl2.org 74 



5. On your lab sheet, record how much time it takes for each canister to blow its lid off. 

6. Rinse the film canisters with water when finished. 

Lab Station F 

More Surface Effects... Is All Water the Same? 

Purpose 

The purpose of the following activities is to provide students with more experience at examining the effects 
of changing surface area to volume ratios. This lab investigates different surface areas for the same volume 
of water on the speed of boiling. 

Safety Precautions 

• Wear safety goggles while conducting this investigation. 

• Be careful when handling glass. 

• Use extra caution when trying to move hot glassware. Either handle with tongs or wait until glassware 
is fully cooled. 

• Be certain to turn off heat source when you have completed this investigation. 

Materials 

• Three very different size beakers or flasks. The goal is to get as different as possible surface area 
among the beakers. 

• Hot plate(s) with enough surface area to accommodate the three beakers/flasks, or 3 Bunsen burners 

• One 100 mL graduated cyclinder 

• A centimeter ruler long enough to measure the diameter of the widest opening of the set of beakers/flasks 

• Tongs designed to use with glassware 

• Clock or watch 

Procedures 

1. Fill in the chart on your lab sheet with the size and type of beaker or flask. 

2. Fill each of the beakers with 100.0 mL of tap water. 

3. Measure the diameter of each of your beakers and record to the nearest mm. For the Erlenmeyer 
flask, if you are using one, measure the diameter of the water when it is in the flask. 

4. Turn on hotplate(s) or Bunsen burners to an equal flame or setting (if using more than one hotplate) 
at the same time. Record the start time on your lab sheet. 

5. Record the time that the water begins to boil in each of the beakers/flasks. Record this time in the 
appropriate column on your lab sheet in the table provided. 

6. Fill out the rest of the lab worksheet for this investigation. 

Teacher Notes 

Students may think that the temperature at which water boils will vary in each of the containers. To avoid 
this mistaken assumption, you may want to have the students at this lab station measure the temperature 
in each of the containers at the beginning of boiling. Students should measure the temperature of the 
water by putting the temperature in the middle of the mass of water, not on the bottom of the beaker or 
flask. 

Lab Station G 

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Surface Area to Volume Effects... Burn Baby Burn! 

Purpose 

These activities are for the purpose of demonstrating the effects of an increased surface area to volume 
ratio on the rate of combustion (burning). 

Safety Precautions 

• Do not pick up any hot items with your fingers or with paper towels. Let cool first. 

• Wear safety goggles. 

• Tie back any long hair. 

Materials 

• One solid rod of steel, about 2 - inches or a steel nail (any size) or steel washer about 11/2 inches. 
These may be purchased at the hardware store. 

• Two sets of tongs 

• Two Bunsen burners and starters 

• A 2 - inch section of steel wool, fine or very fine grade, per group. This can be purchased in a 
hardware store or ordered online from http://www.briwaxwoodcare.com/stelwool.htm 

Procedures 

1. Light the two Bunsen burners to the same level of flame. 

2. Pick up the steel rod or nail with the tongs and heat in the hottest part of the flame for 2 minutes, 
then remove from flame and let cool. Record your observations on your lab sheet. 

3. Pick up the section of steel wool with the tongs and place in the hottest part of the flame for 2 minutes, 
then remove from flame and let cool. Record your observations on your lab sheet. 

4. Once the objects are cooled, deposit any waste into the trash. 

5. Answer questions on your lab sheet. 

Lab Station H 

Surface Area to Volume Effects... Bet I Can Beat'cha! 

Purpose 

The purpose of this lab activity is to demonstrate the effect of varying surface area to volume ratios of the 
same materials on the rate of reaction. 

Safety Precautions 

• Wear goggles during this lab investigation. 

• Don't eat or drink anything at your lab station. 

• Deposit chemical waste according to the instructions of your teacher. Do not flush solution into the 
drain. 

• Use caution when handling glassware. 

Reagent 

• One teaspoon CuCh • 2H2O crystals, per group 
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Materials 

• One teaspoon 

• One glass stirring rod 

• Two 100 mL beakers 

• Two squares, 2 inches x 2 inches, of aluminum foil 

• A pair of tongs 

• Paper towels and a solid waste disposal 

• A clock or watch with a second hand display 

Procedures 

1. Fill each of the 100 mL beakers about half full with tap water. 

2. Add 1 teaspoon of CuCh • IH^O crystals to each of the beakers of tap water and mix well with the 
stirring rod. 

3. Form 1 piece of aluminum foil into a loose ball; leave the other piece as is. 

4. Put each of the aluminum foil pieces into their own beaker. 

5. On your lab sheet, record the time that it takes for each reaction to be complete. 

6. Dispose of solution and waste according to your teacher's instructions. 

Teacher Notes 

Cu 2+ is a heavy metal and must be disposed of properly according to local and state regulations. 
Materials List for All Lab Stations 
Lab Station A: Serial Dilution Lab 

• A stock solution "assigned" the value of 1.0 Molar. You can use unsweetened, scented Kool-Aid. 
Prepare as directed on the package, and then dilute with twice as much water as the directions 
indicate. Alternately, you may use 1 drop of food coloring per liter of water, and add an ester of 
your choice to this mixture. You may have to experiment to make certain that with a 5-part serial 
dilution the odor and color change significantly enough from one test tube to another for students to 
notice. 

• Five test tubes that can hold 10 - mL each 

• One 25 - mL graduated cylinder 

• A test tube holder 

• Grease marker 

• Tap water 

• One 1.0 - mL graduated pipette, plastic or glass 

• A sheet of white paper for background to help students to judge color 

Lab Station B: Ferrofluid Display Cell Lab 

• A plastic 100 mL-graduated cylinder 

• A large empty test tube and stopper 

• A piece of iron (a slug or rod), about 1 - inch in length. This can be purchased from a chemical 
supply house. You may replace a slug of iron with an iron nail or washer, available from a hardware 
store. Note: Most nails are steel rather than iron. 

• Two circle magnets. These magnets come with the ferrofluid display tube. You may add other 
magnets to provide variety for students. 



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• One capped bottle of ferrofluid (nanosized iron particles suspended in a solution). A Ferrofluid Pre- 
form Display Cell can be obtained for $30 plus tax and shipping from: http : //www . teachersource . 
com/catalog/ (Search for item "FF-200") 

You can also check out other ferrofluid products if you are interested. There is an entire kit designed for 
a variety of experiments using ferrofluid and an experiment booklet you can purchase separately. 

Lab Station C: Bubbles Self- Assembly Lab 

• A bubble solution [Bubble Formula: Dawn Ultra or Joy Ultra/ Water (Distilled Water Works 
Best) /Glycerine or White Karo Syrup (Optional) 1 Part/10 Parts/. 25 Parts] 

• Small shallow dish 

• Toothpicks 

• Paper towels 

• Straw (coffee stirrers work best) 

Note: Lab stations D through H are all on surface area to volume effects. 
Lab Station D: Which Shape Can Dissolve the Fastest? 

• Two sugar cubes per group 

• Granulated sugar, about a cup per class 

• A digital balance or scale, with readout to 0.1 gram. A standard laboratory balance can be used 
instead. 

• Two 250 - mL Erlenmeyer flasks 

• A 100 - mL graduated cylinder 

• A grease marker 

• Tap water, about 50 - mL 

• A clock or watch with a second hand 

Lab Station E: Faster Explosion? 

• Two empty film canisters and their lids 

• One tablet of Alka Seltzer® per group 

• One small mortar and pestle 

• Clock or watch with a second hand 

Lab Station F: Is All Water the Same? 

• Three very different size beakers or flasks. The goal is to get as different as possible surface area 
among the beakers. 

• Hot plate(s) with enough surface area to accommodate the three beakers/flasks, or 3 Bunsen burners 

• One 100 mL graduated cyclinder 

• A centimeter ruler long enough to measure the diameter of the widest opening of the set of beakers/flasks 

• Tongs designed to use with glassware 

• Clock or watch 

Lab Station G: Burn Baby Burn! 

• One solid rod of steel, about 2 - inches or a steel nail (any size) or steel washer about 11/2 inches. 
These may be purchased at the hardware store. 

www.ckl2.org 78 



• Two sets of tongs 

• Two Bunsen burners and starters 

• A 2 - inch section of steel wool, fine or very fine grade, per group. This can be purchased in a 
hardware store or ordered online from http://www.briwaxwoodcare.com/stelwool.htm 

Lab Station H: Bet I Can Beat'Cha! 

• Copper(II)chloride dihydrate crystals (C11CI2 • 2H2O). Order from any chemical supply house. 

• A plastic teaspoon that can be used for measuring the crystals 

• One glass-stirring rod. [If a stirring rod is unavailable, the teaspoon may be used to stir. Caution: 
Once the teaspoon has been used to stir the solution, it cannot be used again for measuring out the 
crystals. 

• Two 100 - mL beakers 

• Two squares, 2 inches x 2 inches, of aluminum foil 

• A pair of tongs 

• Paper towels and a solid waste disposal 

• A clock or watch with a second hand display 

Teacher Reading 

Optical Properties 

The optical properties of a material result from the interaction of light with the composition and atomic 
structure of the material. Color, luster, and fluorescence are examples of well-known optical properties. At 
the nanoscale, some interesting optical properties emerge. Gold nanoparticles are one interesting example, 
and zinc oxide is another. These substances exhibit different properties as bulk samples compared to 
nanosized samples, as shown in Table 1, below. 

Table 1.16: Optical properties of gold and zinc oxide for bulk and nano samples 

Substance Macro, or Bulk Sample Nanoparticle Sample 

Gold "Gold" in color "Red" in color 

Zinc Oxide [ZnO) "White" in color "Clear" in color 



What is happening as you go from macro to nano? What underlying principles governing the color changes 
between a bulk sample or a nano sample for the above two materials? 

First, let's consider zinc oxide. Because zinc oxide absorbs ultraviolet light, it can be used in lotions 
to protect against sunburn. Traditional zinc oxide sunscreen is white in color — you may have used this 
yourself or seen it on the noses of life guards and swimmer. "Bulk" ZnO is white in color (e.g. lifeguard 
nose), but nano ZnO is clear. Why is this? The nano ZnO particles don't scatter visible light and they 
also absorb UV rays. Larger particles (greater than 10 -7 meters in diameter) tend to scatter visible light 
but still absorb UV rays. 

In the case of gold, the explanation is a bit more complicated, although the process of making gold 
nanoparticles is centuries old. Long ago, artisans that made stained glass experimented with adding a 
wide variety of metals and metal salts to their molten glass in order to get the glass to take on certain 
colors. They discovered that if they mixed fine particles of gold in, the result was a beautiful ruby color. 
Now these artisans did not know (or really care) exactly why this happened, but it does seem curious 
that gold, a yellow substance, should "stain" glass red. It was not until very recently that the mechanism 

79 www.ckl2.org 



behind this effect became fully understood. 

When light is shone on a piece of metal, the photons kick the electrons in the metal around a bit. In an 
ordinary chunk of metal, electrons are free to move more or less randomly throughout the metal's crystal 
structure. However, if you have a very thin film of metal lying upon an insulator (such as glass), the 
electrons are confined to that thin region. When the light is shone upon them, rather than being free to 
be bumped around randomly, the electrons will move in a coherent wave. 

These coherent waves of electrons are called "surface plasmons." The size of these waves of electrons 
depends primarily upon the thickness of the film. If an incoming photon has just the right wavelength, its 
energy will be completely absorbed by the metal, and turned into a surface plasmon. We call this surface 
plasmon resonance, meaning the incoming photon resonates with the kind of electron waves the film is apt 
to produce. Photons that do not resonate with the metal film will be reflected back. 

The result is that when you shine white light (which consists of photons of many wavelengths) upon such 
a metal film, the film selectively absorbs photons at a certain small range of wavelengths. What we see 
reflected back then is the white light with a particular color "subtracted" from it. For example, if you 
subtract the red photons from white light, the light that is left will look cyan. 

The gold nanoparticle story is basically a case of the larger surface area/volume ratio. If the gold has too 
much interior volume, the effect wouldn't happen; the surface plasmons only occur at interfaces between 
conductors and nonconductors, and if there's a bunch of "non-interface" (interior) conductors, the effect 
basically dissipates. So, since the nanoparticles are pretty much all surface you get the Surface Plasmon 
Resonance (SPR) effect. 

While the stained glass makers only had one technique for creating one particular kind of gold nanopar- 
ticles, modern scientists and engineers can create an infinite variety of them. Now that the mechanism 
is understood, researchers have worked to create nanoparticles that are "tuned" to particular frequencies. 
They can tune the particle by varying its shape, size, and the thickness of the gold film. A recent ap- 
plication of this technology is in cancer treatment. Doctors can embed gold nanoparticles that are tuned 
to absorb infrared light in cancer cells. Then, the doctor shines infrared light upon the tissue. As the 
nanoparticles absorb the infrared light, they heat up. Eventually they heat up enough to destroy the 
cancerous cells. 

Electrical Properties 

Electrical properties of materials are based on the movement of electrons and the spaces, or "holes," they 
leave behind. These properties are based on the chemical and physical structure of the material. It turns 
out that structures at the nanoscale have been found to have some interesting electrical properties. There 
is a plethora of research involving electrical conductivity and carbon nanotubes, in particular. 

A nanotube can be though of as single or multiple sheets of graphite that have been rolled up into a tube, 
as shown in Figure 1, below. 

The electronic properties of the resulting nanotube depend on the direction in which the sheet was rolled 
up. Some nanotubes are metals with high electrical conductivity, while others are semiconductors with 
relatively large band gaps. Which one it becomes depends on way that it is rolled (also called the "chirality" 
of the nanotube"). If it's rolled so that its hexagons line up straight along the tube's axis, the nanotube acts 
as a metal. If it's rolled on the diagonal, so the hexagons spiral along the axis, it acts as a semiconductor. 

Why is this? As shown above, the wall of a nanotube is similar to graphite in structure. Graphite has one 
of the four valence electrons delocalized, and therefore can be shared between adjacent carbons. However, 
it turns out that a single sheet of graphite (also known as graphene) is an electronic hybrid: although 
not an insulator, it is not a semiconductor or a metal either. Graphene is a "semimetal" or a "zero-gap" 
semiconductor. When rolled into a carbon nanotube, it becomes either a true metal or a semiconductor, 
depending on how it is rolled. Shape and geometry make all the difference: diamond, yet another allotrope 

www.ckl2.org 80 




Figure 1.22: A plane of graphite (left) rolled up (middle) gives you a nanotube (right), matching points A 
with A', B with B' and so forth [1]. 



of carbon that has a 3D tetrahedral structure, is an insulator. 

Experiments have been conducted on single walled carbon nanotubes (SWCNT) and multi-walled carbon 
nanotubes (MWCNT) to discover whether electric conductance within them is ballistic or diffuse. In a 
ballistic conductor, all the electrons going into one end come out of the other end without scattering, 
regardless of how far they have to travel. In a diffuse conductor, some of the electrons are scattered before 
they get a chance to exit. Experiments suggest that SWCNTs are diffusive, and MWCNTs are ballistic. 
If adjacent carbon layers in MWCNTs interacted as in graphite, electrons would not be confined to one 
layer, but research suggests that the current mainly flows through the outermost layer. 

One area that is being explored is the possibility of carbon nanotubes being superconductors near room 
temperature. Superconductors are ballistic conductors that also exhibit a resistance of zero, which means 
enormous current flow at tiny voltages. At present, we only know of superconductors that work at extremely 
cold temperatures, below about 130 K(Kelvin; -143° C). Why is superconductivity near room temperature 
such a big deal? If a material could carry current with no resistance at room temperature, no energy 
would be lost as heat. This could lead to faster, lower-power electronics, and the ability to carry electricity 
long distances with 100 per cent efficiency. Although there is no conclusive evidence that nanotubes can 
be superconductors near room temperature, there are some promising indicators. For example, when the 
researchers put a magnetic field across a bundle of MWCNT at temperatures up to 400 K (127° C), the 
bundle generated its own weak, opposing magnetic field. Such a reaction can be a sign of superconductivity. 
When the MWCNTs cooled off and the magnetic field was turned off, they stayed magnetized. This 
could be a result of a lingering current within the tubes because there is little resistance to make it fade 
away — another sign of a superconductor. 

Electrical conductivity within carbon nanotubes remains a mystery. There are many theories and models 
that attempt to predict and describe the electrical conductance of these structures, but they fall short of 
satisfactory explanations, and in fact, sometimes contradict one another. Research continues in this area. 

Carbon nanotubes aren't the only nanoscale structure to exhibit unique electrical properties. For example, 
if extra electrons are added to buckyballs, they can turn into superconductors. DNA may be used in the 
future as electrical conductors. Quantum dots have great potential to behave as very small semiconductors, 
as the electronic structure can be tunable to produce a predictable band gap. Miniature laboratories on a 



81 



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computer chip could employ nanoelectrodes for testing conductance. 

Mechanical Properties 

Mechanical properties are related to the physical structure of a material. Strength and flexibility are 
examples of well-known mechanical properties. At the nanoscale, carbon nanotubes have particularly 
interesting mechanical properties. We will focus on nanotubes here, to illustrate how a nanoscale material 
can exhibit different properties than their bulk counterparts or other forms of carbon that you are familiar 
with, like graphite and diamond. 

As mentioned in the section on electrical properties, a nanotube is similar to graphite in structure. A 
nanotube can be thought of as single or multiple sheets of graphite that have been rolled up into a tube. 
In a sheet of graphite, each carbon atom is strongly bonded to three other atoms, which makes graphite 
very strong in certain directions. However, adjacent sheets are only weakly bound by van der Waals forces, 
so layers of graphite can be slide over one another or be peeled apart, as happens when writing with a 
pencil. The diagram below shows how in graphite, carbon atoms in adjacent layers do not line up and are 
only weakly held together. 




Figure 1.23: Layered lattice structure of graphite, with widely separated planes that are only weakly held 
together by weak van der Waals forces [2]. 



www.ckl2.org 



82 



In contrast, it's not easy to peel a carbon layer from a multiwall nanotube. Nanotubes are very strong — one 
of the strongest materials we know of. They're many times stronger than steel, yet lighter. They are also 
more resistant to damage; that is, they are highly elastic. Nanotubes can be bent to surprisingly large 
angles before they start to ripple, buckle, or break. Even severe distortions won't break them (see below). 




Figure 1.24: A severely distorted nanotube still doesn't break [3]. 

Why are nanotubes so strong? We know that each carbon atom within a single sheet of graphite is 
connected by a strong chemical bond to three neighboring carbon atoms. Why does rolling this strong 
graphite lattice make an even stronger structure? Because of the resulting geometry: Cylinders are one 
the strongest known structural shapes because compared to other geometries, stress on the perimeter is 
more easily distributed throughout the structure. Diamond — a 3D tetrahedral structure where each carbon 
atom forms 4 bonds — is the strongest material known because of its full covalent bonding. But compared 
to nanotubes, diamonds have less interesting properties (e.g., they are insulators, they are not elastic, they 
are denser, and they are very expensive). And some researchers suggest that carbon nanotubes with tiny 
diameters can approach the strength of diamonds! 




Figure 1.25: In diamond, each carbon atom forms bonds, tetrahedrally arranged, to other carbon atoms, 
resulting in a very strongly bonded 3D structure. Very small diameter carbon nanotubes could be as strong 
as diamond. [4] 



Just how strong are nanotubes relative to other materials? Young's Modulus (Y) is one measure of how 
stiff, or elastic, a material is. The higher this value is, the less it deforms when a force is applied. Another 
measure, tensile strength, describes the maximum force that can be applied per unit area before the 
material snaps or breaks. A third interesting measure of a material is the density, which gives you an idea 
of how light the material is. Table 2, below, shows the Young's Modulus, tensile strength, and density of 



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nanotubes compared to other common materials. (GPa stands for gigapascals.) For example, wood is very 
light (low density) but weak (low Young's Modulus and low tensile strength), while nanotubes are many 
times stronger than steel (nanotubes have a higher Young's Modulus and much higher tensile strength) 
and yet much lighter (lower density). Nanotubes also have higher tensile strength even than diamond and 
a similar (slightly lower) elasticity, and yet they are half as dense. 

Table 1.17: Comparison of mechanical properties of various materials. 

Material Young's Modulus (GPa) Tensile Strength (GPa) Density (g/cm3) 

> 30 1.8 

> 30 2.6 

> 20 3.52 
0.2 2.25 
0.4 7.8 
0.008 0.6 



How do researchers measure the stiffness or elasticity of nanotubes? One way is to arrange nantobues like 
trees on a surface so that they are fixed at the bottom, and then measure the amplitude of the thermal 
vibrations of the free ends. Another way is to deposit them on a material that has tiny pores (holes) about 
200 nm wide. Occasionally a nanotube will span a pore by chance, like a bridge over a valley. They will 
then apply an AFM tip to the nanotube to see how much load or force it can take before breaking. 



Single wall nanotube 


-800 


Multi wall nanotube 


-800 


Diamond 


1140 


Graphite 
Steel 


8 
208 


Wood 


16 




Figure 1.26: A carbon nanotube on a porous ceramic membrane, ready for mechanical measurements by 
AFM [5]. 

What are the implications of such strength? Think of what happened when the materials used for tennis 
rackets and golf clubs changed from wood to steel, then to composites of carbon — light but strong carbon 
fibers mixed into another material. The result was lighter, more powerful equipment. Carbon fiber is also 
used in airplanes to make them stronger and lighter. Carbon nanotubes are 10, 000 times thinner than 
commercial carbon fiber, and much stronger. Adding nanotubes to material used for airplanes or cars, for 
example, would make them even stronger yet lighter, so less fuel would be needed to move them, reducing 
operating costs. They could also be used to earthquake-proof homes and bridges. The exceptional strength 
of nanotubes makes them also attractive as tips for scanning probe microscopes. They might even be used 
to link Earth to geostationary orbiting space platforms in the form of a space elevator. 

In summary, the special properties of carbon nanotubes mean that they could be the ultimate high-strength 
fiber. The impacts of light and strong structural materials would be enormous. 

References and Further Reading 

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(Accessed August 2005.) 

• http : //schlecht . gmxhome . de/res/tourOl/tour 13 . html 

• http : //www . everyscience . com/Chemistry/Inorganic/Carbon/a . 1189 . php 

. http://physicsweb.org/articles/world/ll/l/9/l/world / 2Dll / 2Dl /„2D9°/ 2D6 

• http : //www . everyscience . com/Chemistry/Inorganic/Carbon/a . 1189 . php 

• http : //ipn2 . epf 1 . ch/CHBU/NTapplicationsl . htm 

Optical properties 

• Tiny is beautiful: Translating 'nano' into practical: http://www.nytimes.com/2005/02/22/science/ 
22nano.html?pagewanted=l&ei=50 70&en=21806c7a33edd6dl&ex=1115265600 

• Aussies bask in the summer sun, nanopowders protecting their skin: http://www.smalltimes.com/ 
print_doc . cf m?doc_id=5267 

• The surface plasmon spectroscopy is the method of choice in characterizing immobilized molecules 
in their binding activities: http://www.biochem.mpg.de/oesterhelt/xlab/spfs.html 

• Nanoshell-enabled photonics-based imaging and therapy of cancer: http://www.tcrt.org/index. 
cf m?d=3018&#38 ; c=4130&#38 ; p=12032&#38 ; do=detail 

Electrical properties 

• Carbon, its allotropes and structures: http : //www . everyscience . com/Chemistry/Inorganic/Carbon/ 
a. 1189. php 

• Multi-wall carbon nanotubes: http : //pages . unibas . ch/phys-meso/PublicRelations/PhysicsWorld-MWNT . 
htm 

• Carbon nanotubes, materials for the future: http : //www . europhysicsnews . com/f ull/09/article3/ 
article3.html 

• Carbon Nanotubes: http://physicsweb.Org/articles/world/ll/l/9 

• Nanotubes hint at room temperature superconductivity: http://www.newscientist.com/article. 
ns?id=dnl618 

• Berkeley Lab scientists determine electrical properties of carbon-60 molecular layer: http : //enews . 
lbl.gov/Science-Articles/Archive/MSD-C60-molecular-layer.html 

Mechanical properties 

• Multi-wall carbon nanotubes: http : //pages . unibas . ch/phys-meso/PublicRelations/PhysicsWorld-MWNT . 
htm 

• Carbon nanotubes, materials for the future: http : //www . europhysicsnews . com/f ull/09/article3/ 
article3.html 

• Mechanical properties table: /cntproperties.htm#Mechanical%20Properties http : //www . applied-nanotech . 
com/cntproperties.htm#Mechanical°/ 20Properties 

• Mechanical properties: http://ipn2.epfl.ch/CHBU/NTapplicationsl.htm 

• Wilson, M. et. al. (2002). Nanotechnology: Basic science and emerging technologies. Boca Raton, 
FL: CRC Press. 

• Carbon nanotubes: http://physicsweb.Org/articles/world/ll/l/9 

• Simulation predicts diamond-strength carbon nanotube fibers: http : //composite . about . com/library/ 
PR/2001/blpsu5.htm 

85 www.ckl2.org 



Quiz: Teacher Key 

For questions 1-4, choose which force best matches the statement. (1 point each) 

a. gravitational force 

b. electromagnetic forces 

a 1. Describe(s) the attraction of the masses of two particles to each other. 

b 2. Dominate(s) for nanosized objects. 

b 3. Do/does not vary with mass. 

a 4. Stronger for objects with greater mass. 

5. Identify a property that doesn't have meaning when you only have a few nanosized particles, and explain 
why. (2 points) 

Possible answers include boiling point, melting point, vapor pressure. There aren't enough particles for 
the property to emerge. 

6. Compare the surface-to-volume ratios of a large piece of gold with a nanosized piece of gold. (1 point) 

The surface-to-volume ratio for the nanosized piece of gold would be much higher than that for a large 
piece. 

7. Explain in your own words why surface-to-volume ratios are important in determining the properties of 
a substance. You may use a drawing or example to help clarify your explanation. (3 points) 

When surface-to-volume ratio is low, more particles are in the interior of the substance and subject to 
similar forces. When it is high, more particles experience forces from the substance as well as from the 
surrounding material. The effect of this can be seen in a drop of water. The adhesive force of the surface 
can exceed the attraction of the water molecules to each other and cause the drop to flatten out. Reaction 
rates also increase as surface-to-volume ration increases, since a greater percentage of the particles are 
on the surface, which means more particles are immediately available to react, (the collision rate of the 
reacting molecules increases). 

8. Name and explain three properties that are likely to change as when an object is nanosized. You may 
give examples to help clarify your explanation. (3 points) 

Answers may include: optical properties (such as color and transparency), electrical properties (such as 
conductivity), physical properties (such as density and boiling point) and chemical properties (such as 
reactivities and reaction rates). 

9. Explain the concept of electron tunneling and address why this may be a problem for nanosized objects. 
(2 points) 

Electrons can jump across small gaps. This could cause defects in nanoscale structures. 

Tools of the Nanosciences 
Teacher Lesson Plan 

Contents 

• Tools of the Nanosciences: Teacher Lesson Plan 

• Scanning Probe Microscopy: Teacher Reading 

• Scanning Probe Microscopy: PowerPoint with Teacher Notes 

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• Black Box Activity: Teacher Instructions & Key 

• Seeing and Building Small Things Quiz: Teacher Key 

• Optional Extensions for Exploring Nanoscale Modeling Tools: Teacher Notes 

Orientation 

This lesson focuses on two of the most widely used new probe imaging tools: the Atomic Force Microscope 
(AFM) and the Scanning Probe Microscope (SPM). 

• The Scanning Probe Microscopy PowerPoint explains how these two tools work, the difference be- 
tween them, and what you can see and build with them. 

• The Student Reading on Seeing and Building Small Things provides more details on scanning probe 
tools and describes self-assembly as another way to build things. 

• The Black Box Activity gives students the opportunity to use probes to "see" the unknown surface 
of a mystery box and consider firsthand the challenges of using probes. 

• The Seeing and Building Small Things Quiz tests students knowledge of scanning probes and self- 
assembly. 

You may want to extend this lesson beyond one day to incorporate building a model of an AFM. Two 
different strategies are suggested in the Optional Extensions for Exploring Nanoscale Modeling Tools: 
Teacher Notes. 

Essential Questions (EQ) 

What essential questions will guide this unit and focus teaching and learning? 

(Numbers correspond to learning goals overview document) 

4. How do we see and move things that are very small? 

5. Why do our scientific models change over time? 
Enduring Understandings (EU) 

Students will understand: 

(Numbers correspond to learning goals overview document) 

4. New tools for seeing and manipulating increase our ability to investigate and innovate. 
Key Knowledge and Skills (KKS) 

Students will be able to: 

(Numbers correspond to learning goals overview document) 

5. Explain how an AFM and a STM work, and give an example of their use. 
Prerequisite Knowledge and Skills 

• Familiarity with atoms and molecules. 

Related Standards 

. NSES Science and Technology: 12EST2.1, 12EST2.2 

. NSES Science as Inquiry: 12ASI2.3 

. AAAS Benchmarks: 11D Scale #1, 11D Scale #2 



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Table 1.18: 



Day 



Activity 



Time 



Materials 



Prior to this lesson 



Day 1 (50 min) 



Homework: Student 

reading: Seeing and 
Building Small Things 
Teacher Resource: 

Scanning Probe Mi- 
croscopy: Teacher 
Reading 

Show the Scanning 
Probe Microscopy: 

PowerPoint Slides, 

using teacher's notes as 
talking points. 
Highlight the AFM and 
STM, and the relation- 
ship between new tools 
and the ability to gather 
new data and to inno- 
vate using new technolo- 
gies. 



30 min 



30 min 



20 min 



Photocopies of student 
reading 

One copy for the teacher 



Introduction to 

Nanoscience: Pow- 

erPoint Slides 
Computer and projector 



Conduct Black Box Ac- 
tivity 



20 min 



Prepare black boxes ac- 
cording to teacher in- 
structions 

Photocopies of the 
Black Box Activity: 
Student Instructions 
and Questions 



Day 2 (50 min) 



Discuss Black Box Ac- 10 min 
tivity and student read- 
ing: Seeing and Build- 
ing Small Things 

Optional: Extensions Will vary 
for Exploring Nanoscale 
Modeling 

Student Quiz: See- 10 min 
ing and Building Small 
Things 



Teacher notes 



Photocopies of Student 
Quiz Teacher Key for 
correcting Student Quiz 



Scanning Probe Microscopy: Teacher Reading 

Introduction 

In 1981, Gerd Binnig and Heinrich Rohrer, two IBM scientists working in Zurich, Switzerland, invented 
the first scanning tunneling microscope (STM). They were awarded the Nobel Prize in physics for this 
work, which gave birth to the development of a new family of microscopes known as scanning probe 



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microscopes (SPM). All SPMs are based on scanning a probe just above a sample surface while monitoring 
the interaction between the probe and surface. The different types of interactions that are monitored 
are what characterize the different types of scanning probe microscopes. The STM monitors the electron 
tunneling current between a probe and a conducting sample surface, while the more recently developed 
atomic force microscope (AFM) monitors the Van der Waals forces of attraction or repulsion between a 
probe and a sample surface. The advantage of this new family of scanning probe microscopes is that we 
are able to image and manipulate matter as small as 0.1 Angstrom (.01 nm). So how do these probe 
microscopes work to obtain images down to the atomic level? 

The Scanning Tunneling Microscope (STM) 

The STM is based upon a quantum mechanical phenomenon known as electron tunneling. Tunneling is 
the movement of an electron through a classically forbidden potential energy state. A common analogy 
is that of a car of a roller coaster at the bottom of a large hill. Based on classical mechanics, one would 
predict that the car would not make it over the hill if it did not have enough kinetic energy. However, 
viewed from a quantum mechanical viewpoint, an electron is no longer just a particle having either enough 
or not enough energy to make it past a potential energy barrier. Rather, an electron also exhibits wave 
like properties, and as such, the electron is no longer confined to strict energy boundaries. As a wave, 
there is a small but finite probability that the electron can be found on the classically forbidden side of 
the potential energy barrier. When an electron behaves in such a manner, it is said to have tunneled. 

Electron tunneling is the core concept behind the STM. In the STM, a probe, commonly referred to as 
the tip, is brought close to the surface of a sample being examined (see Figure 1). The energy barrier that 
is classically forbidden is the gap (air, vacuum) between the tip and the sample. When the tip and the 
sample are brought within a distance of around 1 nm of each other, tunneling occurs from the tip to the 
sample or vice versa, as long as the sample is an electrical conductor. A current can then be measured as 
result of electrons tunneling. 



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Tunneling 
Current 




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Figure 1.27: Tip and surface and electron tunneling [1] 

The magnitude of the tunneling current is very sensitive to the gap distance between the tip and the sample. 
The tunneling current drops off exponentially with increased gap distance. If the distance is increased by 
as small as 1 Angstrom, the current flow is decreased by an order of magnitude. 

Imaging of the surface of a sample based on electron tunneling current can be carried out in one of two 

ways: 



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1. Constant height mode: The tunneling current is monitored as the tip is scanned across a sample. 
The changes in current give rise to an image of the topography of the sample. 

2. Constant current mode: The tip is moved up and down as the surface changes in order to keep the 
actual tip-to-sample height constant. This maintains a constant current, and the movement of the 
tip is monitored as it is scanned across a sample. The changes in tip height give rise to an image of 
the topography of the sample. This mode is more commonly used. 

STM Tips 

Because of the dependence of the tunneling current upon the tip to sample distance is exponential, it is 
then only the closest atom on the tip of the STM probe that will interact with the sample surface (see 
Figure 2). Tunneling occurs between the electrons of a single atom on the tip of an STM probe, and one 
atom at a time on the sample surface. 

How are these tips made? It is actually not as difficult as one would think. STM tips can be made by 
etching a pit into a crystalline surface such as silicon to make a mold. Then a thin layer of the material 
to be used to make the tip, such as silicon nitride, is placed onto the silicon mold, filling the pit. When 
the silicon nitride layer is removed from the silicon that contained the etch pit, an STM tip is produced. 
Tungsten and platinum are also commonly used to make STM tips. 




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Figure 1.28: An STM tip 



But how do we make sure that the tip is one atom sharp? Actually, is not necessary to worry about placing 
one atom at the very tip. Looking closer at the tip, you will see that there is invariably a crystalline structure 
there (see Figure 3). And if you were to look even closer, at the atomic level, you would in fact see a truly 
atomic tip. Again, because electron-tunneling current changes so dramatically with distance (an increase 
in distance of one Angstrom causes a decrease in tunneling current by a power of ten) , that one atom at 
the tip will produce a tunneling current. Interference from surrounding atoms is negligible due to their 
distance from the sample surface. 

Moving the STM Tip 

In order to get a precise picture of the topography of a sample, the STM tip must scan across the surface 
in increments as small as Angstroms. It is impossible for human manipulation to move a probe at such 
a small scale. To solve this problem, piezoelectric materials are used to move the STM tip in increments 
that the human hand cannot. 

Piezoelectric materials are materials that change shape when a voltage is applied. Some examples of 
piezoelectric materials are ceramics, quartz, human bone, and lead zirconium titanate, which is typically 
used in STMs. The STM tip is connected to a tube containing piezoelectric material. Voltage can then 
be applied to the piezoelectric material, causing fine changes in dimension, which causes the tip to move 
Angstroms at a time. 

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u^u 




Figure 1.29: Zoom in of tip [3] 



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Putting It All Together 

The operation of an STM is based on electron tunneling, which occurs when a tip approaches a conducting 
surface at a very small distance (lnm). The tip is mounted onto a piezoelectric tube, which allows tiny, 
controlled movements of the tip by applying a voltage to the tube. As the tip is scanned along a sample in 
this way, the tip maintains a constant current or a constant tip-to-sample-surface distance. The resulting 
movement of the tip is recorded and displayed revealing a surface picture at the atomic level (see Figure 
4). 



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and scanning unit 




data processing 
and display 



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Figure 1.30: Diagram of an STM [4] 

Challenges in using an STM 

In practice, several challenges arise when using the scanning tunneling microscope. One is vibrational 
interference. Since the tip of an STM is only a nanometer or so from the surface of a sample, it is easy 
to crash the tip into the sample. Any minor cause for vibration, such as a sneeze or motion in the room, 
could result in damaging the tip. 

Contamination from particles in the air such as dust can also be problematic. A small dust particle is 
made up of millions of atoms, and would certainly interfere with the microscope performance. For this 
reason, STMs are commonly run under vacuum. The chemical reactivity of particles in air with the tip or 
sample surface is another reason to scan samples under vacuum. 

One other drawback of the STM is that it is only useful for producing images of conducting or semicon- 
ducting materials because it relies on the tunneling movement of electrons. It is not effective in producing 
images of nonconducting materials. Another scanning microscope, the atomic force microscope, allows us 



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to see nonconducting materials at the atomic level. 

The Atomic Force Microscope (AFM) 

The atomic force microscope (AFM) is another type of scanning probe microscope in the same family 
as STMs. It's based on the same idea: a probe tip scanning a sample to create an image of a sample's 
topography. But rather than monitoring the electron tunneling current between a scanning tip and sample, 
the AFM monitors the forces of attraction and repulsion between a scanning tip and a sample. 

In an AFM, the scanning tip is attached to a spring or cantilever that allows the tip to move as it responds 
to forces of attraction or repulsion it has for a sample surface. The cantilever is a beam around 0.1 mm 
long and a few microns thick. It is supported on one end and has the scanning tip hanging from it on 
the other. Parallel to how the STM works, as the AFM tip is scanned over the sample at constant force, 
the tip attached to a cantilever or spring moves up and down, producing an image of the topography. 
Piezoelectric materials are again used to control the small distances needed to see a sample at the atomic 
level. 

A laser beam is used to measure the movement of the cantilever (see Figure 5). The laser beam is positioned 
so that it reflects off the backside of the cantilever, which usually has a gold coating, behaving like a mirror. 
The reflected beam hits a detector that magnifies and monitors the movement of the cantilever. 

Deciding on a tip to use requires careful consideration. Because it is the mechanical movement of the tip 
itself that ultimately produces the image, the size of the tip used must be chosen carefully. It must be 
small enough to get into all the "nooks and crannies" of a sample surface. The sharpness of a tip must be 
appropriately chosen. 

Position M * 
^ Lasef Detector W 

Figure 1.31: Laser used to measure cantilever movement [5] 

In addition, unlike the STM where only the one atom sharp tip registers surface topography due to electron 
tunneling occurring only over short distances, with the AFM, several atoms near the tip will play a role 
(see Figure 6). Forces of attraction and repulsion occur over longer distances. Several atoms near the tip 
of an AFM will be attracted or repulsed by several atoms on the sample surface. 

The AFM is also more versatile than the STM. It can be adjusted to monitor different forces depending on 
the type of contact the tip has with a sample as well as the type of tip used to scan a sample. Depending 
on the force being monitored, different images of a sample surface can then be produced. 

For example, an AFM can be in "contact mode," where the tip is in direct contact with a surface sample. 
This measures vander Waals forces. A drawback of contact mode is the lateral frictional force that would 
exist as a tip is "dragged" over a sample. To address this, some samples are scanned using the "tapping 

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Figure 1.32: Interatomic interaction for STM (top) and AFM (bottom); shading shows interaction strength 

[6] 



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mode" which oscillates the cantilever tip, while tapping a sample. The benefit of this mode is that frictional 
forces are dramatically reduced. 

Another mode, called the "lift" mode, allows one to image a surface by monitoring magnetic forces and 
electrostatic forces. In addition, because the tip is attached to a cantilever or spring, lateral movement 
and angled deflection can also be measure to produce an image. 



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Figure 1.33: How the AFM works [7] 

Using STMs and AFMs in Nanoscience 

Not only do STMs and AFMs allow us to see images at the nanoscale level, they also enable us to manipulate 
matter at this level. By applying small voltages to an STM tip, atom-by-atom manipulation is possible. 
Being able to change the orientations of atoms (or clumps of atoms) as well as deposit or remove atoms 
(or clumps of atoms) is just the beginning of the development of many future applications. 

References 

(Accessed August 2005.) 



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http : //mrsec . wise . edu/Edetc/modules/MiddleSchool/SPM/MappingtheUnknown . pdf 

http : //mechmat . caltech.edu/~kaushik/park/3-3-0 . htm 

http : //www . chem . qmw . ac . uk/surf aces/scc/scat7_6 . htm 

http : //www . iap . tuwien . ac . at /www/surf ace/STM_Gallery/stm_animated . gif 

http : //www . nanoscience . com/educat ion/AFM . html 

http : //mechmat . caltech.edu/~kaushik/park/3-3-0 . htm 

http : //physchem . ox . ac . uk/~rgc/research/af m/af ml . htm 



Additional Resources 

• http://weizmann.ac. il/Chemical_Research_Support/surf lab/peter/afmworks/ 

• http : //home . earthlink . net/~rpterra/nt/probes . html 

• http : //www . lotoriel . de/pdf _uk/all/pni_tutorial_uk . pdf 



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"Seeing" at the nanoscale 

Scanning Probe Microscopes (SPMs) 

• Monitor the interactions between a probe and a sample surface 

• What we "see" is really an image 

• Two types of microscopy we will look at: 

— Scanning Tunneling Microscope (STM) 

— Atomic Force Microscope (AFM) 

Scanning Tunneling Microscopes (STMs) 

• Monitors the electron tunneling current between a probe and a sample surface 

• What is electron tunneling? 

— Classical versus quantum mechanical model 

— Occurs over very short distances 



STM Tips 

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96 



Scanning Probe 







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Tip and surface and electron tunneling 



Figure 1.34 




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Tunneling current depends on distance 
between tip and surface 



Figure 1.35 



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How do you 
make an STM 
tip '"one 
atom" sharp? 




Let's Zoom In! 




Tunneling current depends on the distance between the STM probe and the sample 



STM Tips II 

• How do you make an STM tip "one atom" sharp? 
Putting It All Together 

• The human hand cannot precisely manipulate at the nanoscale level 

• Therefore, specialized materials are used to control the movement of the tip 

Challenges of the STM 

• Works primarily with conducting materials 

• Vibrational interference 

• Contamination 

— Physical (dust and other pollutants in the air) 

— Chemical (chemical reactivity) 

Atomic Force Microscopes (AFMs) 

• Monitors the forces of attraction and repulsion between a probe and a sample surface 

• The tip is attached to a cantilever which moves up and down in response to forces of attraction or 
repulsion with the sample surface 

— Movement of the cantilever is detected by a laser and photodetector 



AFM Tips 

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98 



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Laser 



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Laser and position detector used to 
measure cantiliver movement 

Figure 1.38 




STMtip 

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Interatomic interaction for 
STM (top) and AFM (bottom). 
Shading shows interaction 
strength. 




AFM tip 



Figure 1.39 



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100 



• The size of an AFM tip must be carefully chosen 
The AFM 



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Specialized materials are again used to manipulate materials at the nanoscale level 



So What Do We See? 




Nickel from an STM 




ZnO from an AFM 



Figure 1.41 



And What Can We Do? 



101 



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Using STMs and AFMs in Nanoscience 

— Allows atom by atom (or clumps of atoms by clumps of atoms) manipulation as shown by the 
images below 





Xenon atoms Carbon monoxide molecules 

Figure 1.42 



Scanning Probe Microscopy Slides: Teacher Notes 

Overview 

This series of slides introduces students to two major types of scanning probe microscopy that are used to see 
and manipulate matter at the nanoscale level. It is recommended that you read the accompanying teacher 
background reading, as it provides more in-depth explanations of the ideas addressed in the PowerPoint 
slides. 

Slide 1: Scanning Probe Microscopy 

Explain to the students that we will cover how scanning probe microscopes can be used to help us "see" 
at the nanoscale level. 

Slide 2: Two Types of Scanning Probe Microscopes (SPMs) 

All SPMs monitor some type of interaction between a probe and a sample surface. The type of interaction 
that is monitored depends on the type of SPM you are using. 

• STMs monitor an electrical current between a probe and a sample surface, meaning it is useful for 
seeing the surface of conducting materials. 

• AFMs monitor the force of attraction or interaction between a probe and a sample surface, and can 
be used to see the surface of all types of materials. 

You may also want to discuss that what we are "seeing" is really an image and how this image may be 
similar or different to what we can see with other tools, such as light microscopes. 

Slide 3: Scanning Tunneling Microscopes (STMs) 

In the classical view of the electron, an electron is a particle that will be found in locations where it has 
enough energy to exist. 

In the quantum mechanical view of the electron, an electron is a wave that primarily exists in areas of 
high probability. However, due to its wave nature, there is a finite possibility that the electron may exist 
in a location beyond high probability energy states, thus allowing for tunneling. Tunneling occurs at very 
short distances, around 1 nm. 

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You may talk about the two different microscopy modes: constant height vs. constant current. You may 
also address the fact that the double-headed arrow signifies that electron tunneling can occur tip to probe 
or probe to tip, depending on how the instrument is biased. But electrons do not tunnel in both directions 
at the same time. 

Slide 4: STM Tips 

Only the atom at the very tip of an STM tip will experience electron tunneling with a sample surface, 
because electron tunneling is exponentially dependent upon distance. 

Slide 5: STM Tips II 

A series of pictures zooming in on an STM tip shows that a one atom sharp tip will almost inevitably be 
naturally occurring. 

Slide 6: Putting it All together 

The animation runs a little slow; you might want to talk over it. 

http : //www . iap . tuwien . ac . at /www/surf ace/STM_Gallery/stm_animated . gif 

The specialized material is referencing piezoelectric materials. You may choose to go into this or skip it 
depending on your class level. 

Slide 7: Challenges of the STM 

Vibrational interference might include sneezing or other air movement in the room that could cause crashing 
of the tip into the sample surface. Running the STM in a vacuum addresses some of the challenges. 

Slide 8: Atomic Force Microscopes (AFMs) 

You might want to start by defining what a cantilever is. AFMs monitor the forces of attraction between a 
scanning probe tip and a sample surface. Because movement of the tip occurs at the nanoscale level-which 
the human eye cannot detect without aid-the movement of a laser beam detects movement in the cantilever. 

Slide 9: AFM Tips 

Unlike STM tips where the electron tunneling will selectively occur between the closest atom on the tip 
and a sample surface, the AFM tip measures interactions between several atoms at the tip. For this reason, 
the size of the tip must be carefully chosen. Smaller and sharper tips yield finer resolution and vice versa. 
You might want to refer back to the Black Box activity and some of the follow-up questions that were 
addressed or discussed there. 

Slide 10: The AFM 

The AFM is a bit more versatile than the STM. Technology has found new ways to monitor different force 
interaction between a tip and a sample surface, leading to their respective images at the atomic level. 

Slide 11: So What Do We See? 

These images of nickel and ZnO are taken from IBM research labs. 
Slide 12: And What Can We Do? 

In general, manipulation is done by applying voltages and charges to an STM tip. 

Black Box Lab Activity: Teacher Instructions & Key 

Purpose 

To use different probes to determine the layout of objects on the bottom surface of a closed box, and to 
consider the limitations and challenges in using probes to "see." The idea is to get students thinking about 
how the scanning probe microscopes give us a picture of the surface of atoms, and to consider some of the 

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basic challenges in scanning probe microscopy. 
Materials 

• One black box 

• One pencil and magnet probe 

• One cotton swab probe 

• One skewer probe 

How to Make a Black Box 

1. Glue different objects to the bottom of each box. Use a variety of objects in various arrangements 
to make this as challenging an activity as appropriate. The class as a whole can have the same 
surface, or each pair can have their own unique surface. Use objects of different compositions and 
shapes — such as pastas, magnets, macaroni noodles, and Q-tips — and glue them in pattern such as 
a square, circle, or triangle. Do not use cotton balls, since they come apart after many jabs with 
probes. Also, use a strong super glue or rubber cement to keep the objects (especially the magnets) 
in place. When arranging, keep in mind that we want the students to be able to deduce the bottom 
surface more accurately when using the smaller barbecue skewer probe. An arrangement that would 
allow this differentiation (such as macaroni noodles 1/4 cm apart instead of 2 ping pong balls 5 inches 
apart) is favorable. 

2. Cut a small (e.g., 1/2 inch) hole in the top of the box, through which students will insert the probes. 
A square box will work best, since it will allow students to reach all parts of the bottom surface from 
a center top hole. If shoeboxes are used, cut more than one hole in the top so that all areas of the 
bottom surface can be reached. 

3. For the pencil and magnet probe, glue an eraser-size magnet onto the eraser end of the pencil. With 
this probe, students will find strong pulls and repulsions by the magnets that are at the bottom of 
your black box. 

4. Prepare enough black boxes and probes for each pair to work with their own set. 

Student Instructions 

1. Obtain from your teacher a box, pencil and magnet probe, a cotton swab probe, and a barbeque skewer 
probe. 

2. Place the pencil and magnet probe into the center hole, and determine as best you can what the surface 
of the bottom of the box looks like. Draw your best guess below. 

A rough sketch of the surface, highlighting any magnets. 

3. Replace the pencil and magnet probe with the cotton swab probe, using the swab end as the probe. 
Is there any additional information you are able to conclude about the surface of the bottom of the box? 
Draw your best guess below. 

A more specific sketch, perhaps identifying some general shapes of the objects. 

4. Replace the cotton swab probe with the barbecue skewer probe, using the pointed end of the skewer as 
the probe. Is there any additional information you are able to conclude about the surface of the bottom 
of the box? Draw your best guess below. 

A more specific drawing, identifying the layout and composition of the surface. 

Questions 

1. Describe the technique you used to investigate the surface of the bottom of the box. 

A systematic survey of the bottom surface, scanning back and forth, row by row. 

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2. What kinds of information about the bottom surface were you able to deduce? 

The layout of the bottom of the box, as well as the composition of the various materials on the bottom 
surface of the box. 

3. How accurate do you think your drawing is? 

The basic layout and the general composition of the different objects are pretty accurate. The specific 
shapes and the texture of the surfaces are some properties that could not accurately be interpreted. 

4. What could you do to get a better idea of what the bottom surface looks like, besides opening the box? 

Use a finer probe, use your fingers as a probe to increase sensitivity, scan the bottom surfaces in smaller 
increments. 

5. What if a ping-pong ball was attached to the probing end of the skewer? How might this have affected 
your interpretations? 

A ping-pong ball would have revealed general information, such as the general layout. The resolution 
would have been less specific and less accurate compared with what the barbecue skewer told us. 

6. What difficulties did you encounter in using this probing technique to "see" the unknown? Or what 
challenges could there be in using such a technique? 

The tip of the probe could be damaged, or the bottom surface could be damaged during probing. The size 
of the probe must be appropriately small. 

Activity adapted from: http : //mrsec . wise . edu/Edetc/modules/MiddleSchool/SPM/MappingtheUnknown . 
pdf 

Seeing and Building Small Things Quiz: Teacher Key 

1. Name the scanning probe instrument that uses electrical current to infer an image of 
atoms. Briefly describe how it works. 

Scanning tunneling microscope (STM): As the STM tip is scanned across a surface, the STM measures 
the flow of electron tunneling current between the tip and the surface. This tunneling current depends 
strongly on the distance between the probe tip and the sample, and thus is sensitive to peaks and valleys 
of the surface. The changes in the strength of this current can be used to create an image of the surface. 

2. Name the scanning probe instrument that reacts to forces inherent in atoms and molecules 
to infer an image of atoms. Briefly describe how it works. 

Atomic force microscope (AFM): As the AFM tip is scanned across a surface, the AFM measures the tiny 
up and down movements of the tip that occur due to the electromagnetic forces of attraction and repulsion 
between the tip and the sample. This movement can be used to create an image of the surface. 

3. Scanning probe instruments can also be used to create things atom by atom. Briefly 
summarize the downside of using such tools to create an aspirin tablet. 

Creating an aspirin table one atom at a time would be very expensive and slow; it would take millions of 
years just to create one tablet because there are a huge number (more than one trillion billion) of aspirin 
molecules in an aspirin tablet. 

4. How does dip pen nanolithography (DPN) work? Using a drawing in your explanation. 

DPN writes structures to a surface the same way that we write ink using a pen. A reservoir of atoms or 
molecules (the "ink") is stored in the tip of an AFM. The tip is then moved across a surface, leaving the 
molecules behind on the surface in specific positions. (Drawing should show the transfer of molecules from 
the AFM tip to the surface.) 

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5. Name two things in nature that are created by self-assembly processes. 

Many answers are possible here; for example, a bubble, snowflake, crystal growth, DNA, cell walls and 
functions, etc. 

6. Circle true or false for each of the following. 

E-beam lithography is a type of self assembly. True False 
One type of self-assembly is crystal growth. True False 
Nanotubes can be grown like trees from seed crystals. True False 
The rules governing self-assembly are fully understood. True False 



Optional Extensions for Exploring Nanoscale Modeling Tools: Teacher 
Notes 

Exploring AFM Models 

Wooden AFM 

Mr. Victor Brandalaise and Dr. Maureen Scharberg at San Jose State University have developed a large- 
scale wood model of an atomic force microscope (AFM). The cost for the materials for this model is 
approximately $30. The wood cantilever has a sewing needle tip, and on top of the cantilever near the tip 
is a mirror. A laser pointer is positioned to beam light from above the cantilever. As the tip skims along a 
surface, such as copper pellets, a piece of textured plastic, or popcorn kernels, the laser beam reflects the 
surface onto a piece of paper. From behind the piece of paper, which is attached to a piece of transparent 
plastic, students can easily trace the amplified surface. For more information, contact Dr. Scharberg at 
(408) 924-4966 or email scharbrg@pacbell.net 

LEGO AFM 

As part of their "Exploring the Nanoworld" program, the Materials Research Science and Engineering 
Center on Nanostructured Materials and Interfaces (MRSEC) at the University of Wisconsin offers mate- 
rials showing how to assemble a large-scale AFM with LEGO bricks; see http : //mrsec . wise . edu/Edetc/ 
LEGO/PDFf iles/2- lapp . PDF . . 

To learn more about exploring the nanoworld with LEGO bricks, or how to order LEGO kits for this 
purpose for your classroom, see http://mrsec.wisc.edu/Edetc/LEGO/index.html 

How Such Models Could Be Used 

Using such models, your students could examine a range of surfaces composed of pure or mixed materials. 
Students could compare traces from the different instruments and, given unidentified traces made by 
other students, try to infer the surface type. These activities could lead to discussions of measurement 
error, identification of impurities in samples, and the advantages and appropriateness of different imaging 
techniques for different surface types. These activities would provide a revealing view of the instruments 
and principles behind them. 

For assessment, students could be asked to depict the functionality of an AFM using the ChemSense 
Animator tool available for free download at http://chemsense.org.. Using ChemSense, students could 
draw the components of the AFM and create an animation that predicts what will happen as the cantilever 
scans across a surface of a sample. In tandem, they could be asked to draw an associated graph that 
illustrates the changes in force over the surface as the tip moves in their animation. Students would 
describe the output of the instrument terms of magnetic repulsion or energy distribution. 

Exploring Self Assembly 

www.ckl2.org 106 





■ -l-i.l 



/AA/ 

/ 



.-•«».< poutoifnrQ 



h| | | |-|r| 






Figure 1 . Wood AFM model. 



Figure 2. Screen shot of a 
ChemSense assessment activity. 



Figure 1.43: Wood AFM model 

(Source: White paper by Bob Tinker, The Concord Consortium) 

The Molecular Workbench (MW) software, available at for both Macintosh and Windows platforms, http: 
//molo. concord.org/software for both Macintosh and Windows platforms, can be used to model nano- 
engineering concepts such as self assembly. Self-assembly is a nano-engineering concept borrowed from 
biological systems. The underlying mechanisms for self-assembly are the general van der Waals mutual 
attraction of all atoms, Coulomb forces due to charged regions of molecules, and shape. 

Shape and Smart Surfaces 

To build in the impact of shape, MW has "Smart Surfaces" that can be drawn by the user. These 
surfaces are actually chains of MW atoms linked together with elastic bonds and covered by a flexible 
surface that hides the atoms. Charge can be added to the periphery of a Smart Surface. The result is 
a good approximation to a large molecule. It can hold its general shape, but it does vibrate, respond to 
temperature, and have both long-range Coulomb forces as well as short-range van der Waals forces. 








Figure 1.44: Smart surfaces can be made to self- assemble. Above is an example of a particularly interesting 
kind of self- assembling object based on nine identical sub-units. 

To run the "Smart Surfaces" model, launch MW from and then look for "self assembly" under "Recent 
models and activities." http://molo.concord.org/software and then look for "self assembly" under 
"Recent models and activities." 



107 



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Figure 1.45: The importance of shape in docking 

The model at the left demonstrates the importance of shape in docking, something similar to self-assembly. 
This model can be heated to separate the two molecules and then both the ball and triangle bounce around. 
On cooling, the triangle eventually finds its way back to the complementary surface through a random 
walk that takes quite a long time. This gives one an appreciation for the time-scale of molecular events of 
this type. 

Applications of Nanoscience 
Teacher Lesson Plan 

Contents 

• Applications of Nanoscience: Teacher Lesson Plan 

• Applications of Nanoscience: PowerPoint with Teacher Notes 

• What's New Nanocat? Poster Session: Teacher Instructions & Rubric 

Orientation 

This lesson introduces students to applications of nanoscience, explores how nanoscale science and engi- 
neering could improve our lives, and describes some potential risks of nanotechnology. 

• The Applications of Nanoscience PowerPoint slides illustrate a variety of current and potential nan- 
otechnology applications. 

• The What's New Nanocat project gives students the opportunity to work in groups to research an 
application of nanoscience, prepare and present it, and give peer feedback. 

Essential Questions (EQ) 

What essential questions will guide this unit and focus teaching and learning? 

www.ckl2.org 108 



(Numbers correspond to learning goals overview document) 

3. Occasionally, there are advances in science and technology that have important and long-lasting effects 
on science and society What scientific and engineering principles will be exploited to enable nanotechnology 
to be the next big thing? 

6. What are some of the ways that the discovery of a new technology can potentially impact our lives? 

Enduring Understandings (EU) 

Students will understand: 

(Numbers correspond to learning goals overview document) 

1. The study of unique phenomena at the nanoscale could change our understanding of matter and lead 
to new questions and answers in many areas, including health care, the environment, and technology. 

Key Knowledge and Skills (KKS) 

Students will be able to: 

(Numbers correspond to learning goals overview document) 

3. Describe an application (or potential application) of nanoscience and its possible effects on society. 

4. Compare a current technology solution with a related nanotechnology-enabled potential solution for the 
same problem 

Prerequisite Knowledge and Skills 

• Ability to research topics independently (for optional activity). 
Related Standards 

. NSES Science and Technology: 12EST2.2, 12EST2.4 

• History and Nature of Science. 12GHNS3.3 
. NSES Science as Inquiry: 12ASI2.3 

Table 1.19: 

Day Activity Time Materials 

Day 1 (35 min) Show the PowerPoint 20 min PowerPoint slides: 

slides: Applications Applications of 

of Nanoscience, using Nanoscience 

teacher's notes as talk- Computer and projector 

ing points. Describe 
and discuss interac- 
tively with students the 
examples shown of pos- 
sible applications. Try 
to stimulate student 
interest! 



109 www.ckl2.org 



Table 1.19: (continued) 



Day 



Activity 



Time 



Materials 



Days 2-4 (full class) 



Day 5 (full class) 



What's New Nanocat? 15 min 
Assign or allow students 
to choose the nanotech- 
nology topic they want 
to investigate for the 
project. Students will 
work in groups of 3 or 
4. 



Students conduct in- 3 days 
dependent investigation 
and prepare a presenta- 
tion, in groups, on cho- 
sen/assigned topic. 



Students make their 1 day 
presentations to the 
class. Class mem- 

bers discuss and ask 
questions. 



What's New Nanocat? 
Teacher Instructions 
and Rubric 

Prepare a sign-up sheet 
for each student group 
to indicate their cho- 
sen topic and the names 
of all students in their 
group. 

Computers with inter- 
net connection, journal 
articles, library. 
Materials for making 
a poster presentation 
using PowerPoint or 
posters. 

Copies of the What's 
New Nanocat? Poster 
Session: Peer Feedback 
Form 

Scoring rubric will be 
used to score student 
presentations. 
May require computer 
and projector for those 
students wishing to 
present their topic 
using PowerPoint. 
You may want to dis- 
play paper posters or 
share PowerPoint slide 
presentations. 



Applications of Nanoscience 

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110 




How might nanoscale science and engineering improve our lives? 
Potential Impacts of Nanotechnology 

• Materials 

— Stain-resistant clothes 

• Health Care 

— Chemical and biological sensors, drugs and delivery devices 

• Technology 

— Better data storage and computation 

• Environment 

— Clean energy, clean air 



r i 





Thin layers of gold are used Carbon nanotubes can be 
in tiny medical devices used for H fuel storage 

Materials: Stain Resistant Clothes 



Possible entry point for 
nanomedical device 



• Nanofibers create cushion of air around fabric 

— 10 nm carbon whiskers bond with cotton 

— Acts like peach fuzz; many liquids roll off 

Materials: Paint That Doesn't Chip 

• Protective nanopaint for cars 

— Water and dirt repellent 

— Resistant to chipping and scratches 



111 



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Nano pants that refuse to stain; Nano-Care fabrics with water, cranberry juice, 
Liquids bead up and roll off vegetable oil, and mustard after 30 minutes 

(left) and wiped off with wet paper towel (right) 

Figure 1.46 




Mercedes covered with tougher, 
shinier nanopaint 

Figure 1.47 



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112 



— Brighter colors, enhanced gloss 

— In the future, could change color and self-repair? 

Environment: Paint That Cleans Air 




Buildings as air purifiers? 



Figure 1.48 



Nanopaint on buildings could reduce pollution 

— When exposed to ultraviolet light, titanium dioxide (T1O2) nanoparticles in paint break down 
organic and inorganic pollutants that wash off in the rain 

— Decompose air pollution particles like formaldehyde 



Environment: Nano Solar Cells 




Su-.-T'l 



t- cvt-ooc 



T 



— '- 

Nvxvcdi 



Nano solar cell: Inorganic nanorods embedded in semiconducting 
polymer, sandwiched between two electrodes 

Figure 1.49 



• Nano solar cells mixed in plastic could be painted on buses, roofs, clothing 
— Solar becomes a cheap energy alternative! 

Technology: A DVD That Could Hold a Million Movies 



::; i-i 



Current CD and DVD media have storage scale in micrometers 

113 



www.cki2.0rg 




•;: i n 



DVD 



'V* .i.V* 



i ■ 
Si (111) -Au 5x2 




1Q |.m 



1i nrr 



Figure 1.50 

• New nanomedia (made when gold self-assembles into strips on silicon) has a storage scale in nanome- 
ters 

— That is 1,000 times more storage along each dimension (length, width) or 1,000,000 times 

greater storage density in total! 

Technology: Building Smaller Devices and Chips 

• Nanolithography to create tiny patterns 

— Lay down "ink" atom by atom 

Health Care: Nerve Tissue Talking to Computers 

• Neuro-electronic networks interface nerve cells with semiconductors 

— Possible applications in brain research, neurocomputation, prosthetics, biosensors 

Health Care: Detecting Diseases Earlier 

• Quantum dots glow in UV light 

— Injected in mice, collect in tumors 

— Could locate as few as 10 to 100 cancer cells 



Health Care: Growing Tissue to Repair Hearts 
www.ckl2.org 114 




Mona Lisa, 8 microns tall, 
created byAFM nanolithography 



V 



ATM Tip 



^\> 



Wmtg a-tcttfl 



•WKKIMH 




Transporting molecules to a surface 
by dip-pen nanolithography 



Figure 1.51 








Snail neuron grown on a chip 
that records the neuron's activity 

Figure 1.52 



mi 

Quantum Dots: Nanometer-sized crystals 
that contain free electrons and emit 
photons when submitted to UV light 




Early tumor detection, 
studied in mice 



Figure 1.53 



115 



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Nanofibers help heart muscle grow in the lab 

— Filaments 'instruct' muscle to grow in orderly way 

— Before that, fibers grew in random directions 




Cardiac tissue grown with the help 
of nanofiber filaments 

Figure 1.54 
Health Care: Preventing Viruses from Infecting Us 

• Nanocoatings over proteins on viruses 

— Could stop viruses from binding to cells 

— Never get another cold or flu? 

Health Care: Making Repairs to the Body 

• Nanorobots are imaginary, but nanosized delivery systems could... 

— Break apart kidney stones, clear plaque from blood vessels, ferry drugs to tumor cells 

Pause to Consider 

How delicate are nanoscale - sized objects? 

How well do we understand the environmental and health impacts of nanosized clusters of particles? 

Nanodevices Are Sensitive! 

• Radiation particles can cause fatal defects 

— Development requires very clean environments 

— Redundant copies compensate for high defect rate 



Potential Risks of Nanotechnology 

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116 




Gold tethered to the 
protein shell of a virus 




Influenza virus: Note proteins 
on outside that bind to cells 



Figure 1.55 




Figure 1.56 



117 



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Pit created by nuclear radiation 

(an alpha particle) hitting a mica surface 

Figure 1.57 

• Health issues 

— Nanoparticles could be inhaled, swallowed, absorbed through skin, or deliberately injected 

— Could they trigger inflammation and weaken the immune system? Could they interfere with 
regulatory mechanisms of enzymes and proteins? 

• Environmental issues 

— Nanoparticles could accumulate in soil, water, plants; traditional filters are too big to catch 
them 

• New risk assessment methods are needed 

— National and international agencies are beginning to study the risk; results will lead to new 
regulations 

Summary: Science at the Nanoscale 

• An emerging, interdisciplinary science 

— Integrates chemistry, physics, biology, materials engineering, earth science, and computer science 

• The power to collect data and manipulate particles at such a tiny scale will lead to 

— New areas of research and technology design 

— Better understanding of matter and interactions 

— New ways to tackle important problems in healthcare, energy, the environment, and technology 

— A few practical applications now, but most are years or decades away 

Teacher Notes 

Overview 

This series of slides introduces students to some of the areas thought to have great potential for impact on 
our lives through nanotechnology innovations. Example applications and references for further information 
are provided. Don't feel that you need to show all of these slides. Show the ones that you think will most 
interest and reach your particular students. 

Slide 1: Applications of Nanoscience 

Explain to students that you're going to present several examples of how new innovations in nanotechnology 
might impact our lives. 

www.ckl2.org 118 



Slide 2: Potential Impact of Nanotechnology 

Point out that tools for manipulating materials are becoming more sophisticated and improving our un- 
derstanding of how atoms and molecules can be controlled. This will lead to significant improvements in 
materials, and, in turn, to new products, applications, and markets that could have revolutionary impact 
on our lives. 

This presentation will focus on innovations related to nano materials, the environment, technology, and 
healthcare. A few of these products being commercialized now, but most are in research labs or are 
envisioned for the distant future. 

References: 

• Nanotechnology now - Current uses: htm http://www.nanotech-now. com/currentuses. htm 

• Nanoscale Science and Engineering Center: http://www.mos.0rg/cst/section/2.html 

• Book: "The Next Big Thing Is Really Small: How Nanotechnology Will Change The Future Of Your 
Business" by Jack Uldrich and Deb Newberry (2003) 

Slide 3: Materials: Stain Resistant Clothes 

Manufacturers are embedding fine-spun fibers into fabric to confer stain resistance on khaki pants and 
other products. These "nano whiskers" act like peach fuzz and create a cushion of air around the fabric so 
that liquids bead up and roll off. Each nanowhisker is only ten nanometers long, made of a few atoms of 
carbon. To attach these whiskers to cotton, the cotton is immersed in a tank of water full of billions of 
nanowhiskers. Next, as the fabric is heated and water evaporates, the nanowhiskers form a chemical bond 
with cotton fibers, attaching themselves permanently. The whiskers are so tiny that if the cotton fiber 
were the size of a tree trunk, the whiskers would look like fuzz on its bark. 

Nano-resistant fabric created by NanoTex is already available in clothing available in stores like Eddie 
Bauer, The Gap, and Old Navy. This innovation will impact not only khaki wearers, but also dry cleaners 
who will find their business declining, and detergent makers who will find less of their project moving off 
the shelf. 

References: 

• Fancy pants: http: //www. sciencentral. com/articles/view. php3?article_id=218391840& 
cat=3_5 

• NanoTex lab activity: http : //mrsec . wise . edu/Edetc/IPSE/educators/act ivities/nanoTex . html 

Slide 4: Materials: Paint That Doesn't Chip 

Nanopaints are ceramic based coatings that make the paint a lot more durable and resistant to rock chips 
and scratches. In addition to holding up better to weathering, nanopaints have richer and brighter colors 
than traditional pigments. In the future, nanopaints may also even change color 

References: 

• Mercedes-Benz Nano Paint (3 page article on benefits, material, and paint process): http: //www. 
autol23 . com/en/info/news/news , view . spy?art id=21942&#38 ; pg=l 

Slide 5: Environment: Paint That Cleans Air 

Chinese scientists have announced that they have invented nanotech-based coating material that acts as 
a permanent air purifier. If the coating proves to be effective at air cleaning, it will be gradually used on 
buildings to improve air quality. The core of the material is a titanium-dioxide-based compound developed 

119 www.ckl2.org 



using advanced nanotechnology. Exposed under sunlight, the substance can automatically decompose 
ingredients like formaldehyde that cause air pollution. 

References: 

• Paint to help clean and purify the air: http://english.eastday.com/eastday/englishedition/ 
metro/user object lai710823.html 

Slide 6: Environment: Nano Solar Cells 

Enough energy from the sun hits the earth every day to completely meet all energy needs on the planet, 
if only it could be harnessed. Doing so could wean us off of fossil fuels like oil and provide a clean 
energy alternative. But currently, solar-power technologies cost as much as 10 times the price of fossil fuel 
generation. Chemists at U.C. Berkeley are developing nanotechnology to produce a photovoltaic material 
that can be spread like plastic wrap or paint. These nano solar cells could be integrated with other building 
materials, and offer the promise of cheap production costs that could finally make solar power a widely 
used electricity alternative. 

Current approaches embed nanorods (bar-shaped semiconducting inorganic crystals) in a thin sheet (200 nanometers 
deep) of electrically conductive polymer. Thin layers of an electrode sandwich these nanorod-polymer com- 
posite sheets. When sunlight hits the sheets, they absorb photons, exciting electrons in the polymer and 
the nanorods, which make up 90 percent of the composite. The result is a useful current that is carried 
away by the electrodes. Eventually, nanorod solar cells could be rolled out, ink-jet printed, or even painted 
onto surfaces, so that even a billboard on a bus could be a solar collector. 

References: 

• Painting on solar cells: http: //www. calif orniasolarcenter. org/solareclips/2003. 01/20030128-6. 
html 

• Cheap, plastic solar cells may be on the horizon: http : //www . berkeley . edu/news/media/releases/ 
2002/03/28_solar . html 

• New nano solar cells to power portable electronics: http://www.californiasolarcenter.org/ 
solareclips/2002 . 04/20020416-7 . html 

Slide 7: Technology: A DVD That Could Hold a Million Movies 

In 1959, Richard Feynman asked if we could ever shrink devices down to the atomic level. He couldn't find 
any laws of physics against it. He calculated that we could fit all printed information collected over the 
past several centuries in a 3 - dimensional cube smaller than the head of a pin. How far have we come? 
A 2 - dimensional version of Feynman's vision is in research labs. The picture on this slide illustrates the 
potential of nano-devices for data storage. On the left are images of two familiar data storage media: the 
CD-ROM and the DVD. On the right is a self- assembled memory on a silicon surface, formed by depositing 
a small amount of gold on it. It looks like CD media, except that the length scale is in nanometers, not 
micrometers. So the corresponding storage density is a million times higher! The surface automatically 
formats itself into atomically-perfect stripes (red) with extra atoms on top (white). These atoms are neatly 
lined up at well-defined sites along the stripes, but occupy only about half of them. It is possible to use 
the presence of an atom to store a 1, and the absence to store a 0. The ultimate goal would be to build 
a data storage medium that needs only a single atom per bit. The big question is how to write and read 
such bits efficiently. 

References: 

• Franz J. Himpsel's web site: http://uw.physics.wisc.edu/-himpsel/nano.html 
www.ckl2.org 120 



• R. Bennewitz et al., "Atomic scale memory at a silicon surface" Nanotechnology 13, 499 (2002) 

Slide 8: Technology: Building Smaller Devices and Chips 

A technique called nanolithography lets us create much smaller devices than current approaches. For 
example, the Atomic Force Microscope (AFM) nanolithography image of the Mona Lisa was created by a 
probe oxidation technique. This technique can be used to further miniaturize the electrical components 
of microchips. Dip pen nanolithography is a 'direct write' technique that uses an AFM to create patterns 
and to duplicate images. "Ink" is laid down atom by atom on a surface, through a solvent — often water. 

References: 

• AFM Oxidation nanolithography Principles/Lithographies/AFM_Oxidation_Lithography_mode37.html 
http : //www . ntmdt . ru/SPMTechniques/ Principles/Lithographies/AFM_Oxidation_Lithography_- 
mode37.html 

• Dip pen nanolithography: http://www.chem.northwestern.edu/~mkngrp/dpn.htm 

Slide 9: Health Care: Nerve Tissue Talking to Computers 

Researchers are studying the electrical interfacing of semiconductors with living cells-in particular, neu- 
rons-to build hybrid neuro-electronic networks. Cellular processes are coupled to microelectronic devices 
through the direct contact of cell membranes and semiconductor chips. For example, electrical interfacing 
of individual nerve cells and semiconductor microstructures allow nerve tissue to directly communicate 
their impulses to computer chips. Pictured is a snail neuron grown on a CMOS chip with 128 x 128 
transistors. The electrical activity of the neuron is recorded by the chip, which is fabricated by Infineon 
Technologies. This research is directed (1) to reveal the structure and dynamics of the cell-semiconductor 
interface and (2) to build up hybrid neuroelectronic networks. Such research explores the new world at the 
interface of the electronics in inorganic solids and the ionics in living cells, providing the basis for future 
applications in medical prosthetics, biosensorics, brain research and neurocomputation. 

References: 

• Nanopicture of the day from Peter Fromherz: http : //www . nanopicof theday . org/2003Pics/Neuroelectronic' 
20Interf ace . htm 

• Max Planck research: http://www.biochem.mpg.de/mnphys/ 

Slide 10: Health Care: Detecting Diseases Earlier 

Quantum dots are small devices that contain a tiny droplet of free electrons, and emit photons when 
submitted to ultraviolet (UV) light. Quantum dots are considered to have greater flexibility than other 
fluorescent materials, which makes them suited for use in building nano-scale applications where light is 
used to process information. Quantum dots can, for example, be made from semiconductor crystals of 
cadmium selenide encased in a zinc sulfide shell as small as 1 nanometer (one-billionth of a meter) . In UV 
light, each dot radiates a brilliant color. 

Because exposure to cadmium could be hazardous, quantum dots have not found their way into clinical 
use. But they have been used as markers to tag particles of interest in the laboratory. Scientists at 
Georgia Institute of Technology have developed a new design that protects the body from exposure to 
the cadmium by sealing quantum dots in a polymer capsule. The surface of each capsule can attach to 
different molecules. In this case, they attached monoclonal antibodies directed against prostate-specific 
surface antigen, which is found on prostate cancer cells. The researchers injected these quantum dots into 
live mice that had human prostate cancers. The dots collected in the tumors in numbers large enough to 
be visible in ultraviolet light under a microscope. Because the dots are so small, they can be used to locate 

121 www.ckl2.org 



individual molecules, making them extremely sensitive as detectors. Quantum dots could improve tumor 
imaging sensitivity tenfold with the ability to locate as few as 10 to 100 cancer cells. Using this technology, 
we could detect cancer much earlier, which means more successful, easier treatment. 

References: 

• Quantum dots introduction: http://vortex.tn.tudelft.nl/grkouwen/qdotsite.html 

• Lawrence Livermore Labs work in quantum dots: http://www.llnl.gov/str/Lee.html 

• Quantum dots light up prostate cancer: http://www.whitaker.org/news/nie2.html 

Slide 11: Health Care: Growing Tissue to Repair Hearts 

Cardiac muscle tissue can be grown in the lab, but the fibers grow in random directions. Researchers at 
the University of Washington are investigating what type of spatial cues they might give heart- muscle cells 
so that they order themselves into something like the original heart-muscle tissue. Working with one type 
of heart muscle cell, they have been able to build a two-dimensional structure that resembles native tissue. 
They use nanofibers to "instruct" muscle cells to orient themselves in a certain way. They have even able 
to build a tissue-like structure in which cells pulse or 'beat' similar to a living heart. 

This image on this slide shows cardiac tissue grown with the aid of nanofiber filaments. It displays well- 
organized growth that is potentially usable to replace worn out or damaged heart tissue. The ultimate 
goal of building new heart-muscle tissue to repair and restore a damaged human heart is a long way off, 
but there have been big advances in tissue engineering in recent years. 

References: 

• University of Washington cardiac muscle work: http : //www . Washington . edu/admin/f inmgmt/annrpt/ 
mcdevitt .htm 

Slide 12: Health Care: Preventing Viruses from Infecting Us 

If we could cover the proteins that exist on the influenza virus, we could prevent the virus from recognizing 
and binding to our body cells. We would never get the flu! A protein recognition system has already been 
developed. More generally, this work suggests that assembled virus particles can be treated as chemically 
reactive surfaces that are potentially available to a broad range of organic and inorganic modification. 

References 

• Virus nanoblocks: http://pubs.acs.org/cen/topstory/8005/8005notw2.html 

Slide 13: Health Care: Making Repairs to the Body 

The image on this slide depicts what one nanoscientist from the Foresight Institute imagines might be 
possible one day in the far future. It shows how a nanorobot could potentially interact with human cells. 
When people hear of nanotechnology from science fiction, this is often the form that it takes. But we may 
not know for decades whether such a probe is even possible. But if they are developed someday, they could 
be used to maintain and protect the human body against pathogens. For example, they could (1) be used 
to cure skin diseases (embedded in a cream, they could remove dead skin and excess oils, apply missing 
oils), (2) be added to mouthwash to destroy bacteria and lift plaque from the teeth to be rinsed away, (3) 
augment the immune system by finding and disabling unwanted bacteria and viruses, or (4) nibble away 
at plaque deposits in blood vessels, widening them to prevent heart attacks. 

References: 

• Nanorobots: medicine of the future: http://www.ewh.ieee.org/rl0/bombay/news3/page4.html 
www.ckl2.org 122 



• Robots in the body: http://www.genomenewsnetwork.org/articles/2004/08/19/nanorobots. 
php 

• Drexler and Smalley make the case for and against molecular assemblers http://pubs.acs.org/ 
cen/coverstory/8148/8148counterpoint . html 

Slide 14: Pause to Consider 

The next 2 slides focus on the delicate nature of nanosized objects, the potential risks of nanotechnology 
to humans and the environment, and the need study the risks and regulate the development of products 
that contain nanoparticles. 

Slide 15: Nanodevices Are Sensitive! 

Because of their small size, nanodevices are very sensitive and can easily be damaged by the natural 
environmental radiation all around us. In the picture for this example, we see a pit caused by an alpha 
particle hitting the surface of mica. An alpha particle is a highenergy helium nucleus that is the lowest- 
energy form of nuclear radiation. Alpha particles are also the particles that Rutherford used for the gold 
foil experiment in which he discovered the arrangement of protons within the atom that is now commonly 
known as the nucleus. The impact of alpha particles on a solid surface can cause physical damage by 
causing other atoms in the surface to be moved out of place. These types of defects can be potentially fatal 
in high-density electronics and nanodevices. To compensate, extremely clean manufacturing environments 
and very high redundancy — perhaps millions of copies of nanodevices for a given application — are required. 

References: 

• Fei and Fraundorf on Alpha recoil pits: http://www.nanopicoftheday.org/2004Pics/February2004/ 
AlphaRecoil . htm 

• Nano memory scheme handles defects: fects_Brief_090804.html http://www.trnmag.com/Stories/ 
2004/090804/Nano_memory_scheme_handles_de fects_Brief_090804.html 

Slide 16: Potential Risks of Nanotechnology 

Nanotechnology's potential is encouraging, but the health and safety risks of nanoparticles have not been 
fully explored. We must weigh the opportunities and risks of nanotechnology in products and applications 
to human health and the environment. Substances that are harmless in bulk could assume hazardous 
characteristics because when particles decrease in size, they become more reactive. A growing number of 
workers are exposed to nanoparticles in the workplace, and there is a danger that the growth of nanotech- 
nology could outpace the development of appropriate safety precautions. Consumers have little knowledge 
of nanotechnology, but worries are already beginning to spread. For example, environmental groups have 
petitioned the Food and Drug Administration to pull sunscreens from the market that have nano-size tita- 
nium dioxide and zinc oxide particles. As nanotechnology continues to emerge, regulatory agencies must 
develop standards and guidelines to reduce the health and safety risks of occupational and environmental 
nanoparticle exposure. 

References: 

• Risks of nanotechnology: http://en.wikipedia.org/wiki/Nanotechnology 

• Overview of nanotechnology: Risks, initiatives, and standardization: http://www.asse.org/nantechArticle. 
htm 

Slide 17: Summary: Science at the Nanoscale 

Nanoscience is an emerging science that will change our understanding of matter and help us solve hard 
problems in many areas, including energy, health care, the environment, and technology. With the power 

123 www.ckl2.org 



to collect data and to manipulate particles at such a tiny scale, new areas of research and technology design 
are emerging. Some applications — like stain resistant pants and nanopaint on cars — are here today, but 
most applications are years or decades away. But nanoscience gives us the potential to understand and 
manipulate matter more than ever before. 

Nanoscience is truly an interdisciplinary science. Progress in nanoscale science and technology results from 
research involving various combinations of biology, chemistry, physics, materials engineering, earth science, 
and computer science. Nanoscience also provides a way to revisit the core concepts from these domains 
and view them through a different lens. Learning about nanoscience can support understanding of the 
interconnections between the traditional scientific domains and provide compelling, realworld examples of 
science in action. 

What's New Nanocat? Poster Session: Teacher Instructions &; Rubric 

Summary 

Students will work in pairs to create a poster that compares a current technology with a related, new 
nanotechnology application. A list of applications (including references) to choose from will be provided 
to the students. The list is based on applications that have been mentioned or discussed in class or in 
associated readings (e.g., nanotubes as stronger tethers, nano solar cells as omnipresent collectors, stain- 
resistant nanopants). 

The student will assume the role of a scientist working on the new nanotechnology application, and explain 
the proposed usage of the new technology in a poster session. The student will produce a poster showing 
a current technology and how it is used; a new, related nanotechnology and how it is proposed to be used; 
how the new nanotechnology works; and how the new nanotechnology will help improve understanding or 
solve a problem. 

The posters will be displayed in class and the students will explain the technology by explaining the poster. 
This could be done in a science fair type arrangement or in class as a presentation. The presentation must 
include diagrams along with written descriptions to help someone gain a better understanding of the 
science. It can also optionally include animations. 

Time Frame: 2-3 hours to create posters, 1 hour for poster session 

Criteria for Evaluation 

The poster will be graded based on a rubric. The student's discussion and answers to questions during the 
poster session will influence the grade. The students must demonstrate understanding of the technology 
s/he is explaining. 

Relevant Learning Goals 

• Nanoscience is an emerging science that could vastly change our understanding of matter and lead to 
new questions and answers in many areas, including health care, the environment, and technology. 

• Nanotechnology focuses on manipulating matter at the nanoscale to create structures that have novel 
properties or functions. 

Required Resources 

• List of applications from which students can choose their poster topic. 

• Access to the Web to research the technologies, find relevant diagrams, etc. 

• Optional use of ChemSense to create diagrams or animations to illustrate how the technologies work 

• Optional access to PowerPoint or other slide creation tool for creating poster pages 

www.ckl2.org 124 



If posters are to be displayed in the classroom, access to posterboard, paper, and printer, and glue 
or tape are required. 

Table 1.20: Rubric for NanoCat Poster Evaluation 



Novice (1) Absent, 
inaccurate, or con- 
fused 



Apprentice (2) 
Partially devel- 
oped 



Skilled (3) Ade- 
quately developed 



Masterful (4) Fully 
developed 



Written explana- 
tions 



Graphic explana- 
tions 



Accuracy and Re- 
search 



Attractiveness 



Attribution 



Oral Team Presen- 
tation 



Shows little un- 
derstanding or 
major misun- 
derstanding of 
ideas or processes. 
Concepts, data, 
and arguments are 
inadequate. Many 
grammatical 
errors. 

Shows little under- 
standing of pro- 
cesses, or inade- 
quate for address- 
ing the applica- 
tion. 

Misunderstanding 
of nanoscience 

is evident in 
inaccurate ex- 

planations or 

science-fiction-like 
ideas presented 
as facts. Demon- 
strates little or no 
research. 
Distractingly 
messy or bad 
design. 



Diagrams and text 
do not have any 
source citations. 

Most members did 
not participate, 
communication 
was unclear, hard 
to hear, little eye 
contact, answered 
few questions. 



Shows limited 

understanding or 
misunderstand- 
ing of key ideas. 
Concepts, data, 
and arguments are 
simple or some- 
what inadequate. 
Some grammar 
errors. 

Shows limited 

understanding of 
ideas. Graphics 
are crude, simple, 
or reveal a key 
misunderstanding. 
Limited under- 
standing is evident 
by some inaccu- 
rate or simple 
explanations, or 
futuristic ideas 
confused with 

fact. Demon- 

strates average 
research. 

Somewhat orga- 
nized, acceptable 
design, but messy. 



More than two dia- 
grams and text do 
not have source ci- 
tations. 

Few members 

participated, com- 
munication was 
somewhat unclear, 
answered half of 
audience questions 
well. 

125 



Shows a solid 
understanding of 
ideas, no misun- 
derstanding of key 
ideas. Concepts, 
data, arguments 
are appropri- 

ate. Grammar is 
mostly correct. 

Shows solid un- 
derstanding. 
Graphics show no 
misunderstanding 
of key ideas, are 
not overly simple. 
Shows solid un- 
derstanding with 
clear explanations 
with sound sci- 
entific basis, no 
clear inaccuracies. 
Demonstrates 
solid research. 



Solid organization, 
with good design, 
layout, and neat- 
ness. 

All but one or two 
diagrams and text 
have source cita- 
tions. 

Most members 
participated, com- 
municated clearly, 
answered most 
audience questions 
reasonably well. 



Shows clear, 

complete, and 

sophisticated un- 
derstanding of 
ideas, advanced 
beyond the grasp 
usually found at 
this age. Easy to 
read, with correct 
grammar. 
Shows clear, 

complete, and 

sophisticated 
understanding 
of ideas and 
processes. 
Shows sophis- 

ticated under- 

standing based on 
current facts and 
scientific theory, 
and futuristic 

ideas presented 
as such. Demon- 
strates extensive 
research. 

Sophisticated pre- 
sentation that is 
well organized and 
neat, with good 
design and layout. 
All text and 
borrowed dia- 

grams have source 
citations. 

All team members 
participated, com- 
municated clearly, 
kept eye contact, 
and answered 

audience questions 
well. 

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Table 1.20: (continued) 



Novice (1) Absent, Apprentice (2) Skilled (3) Ade- Masterful (4) Fully 
inaccurate, or con- Partially devel- quately developed developed 
fused oped 



One-Day Introduction to Nanoscience 
Teacher Lesson Plan 

Contents 

• One-Day Introduction to Nanoscience: Teacher Lesson Plan 

• One-Day Introduction to Nanoscience: Teacher Demonstration Instructions 

• One-Day Introduction to Nanoscience: PowerPoint with Teacher Notes 

Remaining materials (the introductory student readings, worksheets, worksheet keys and scale diagram) 
can be found in Lesson 1: Introduction to Nanoscience. 

Orientation 

This abridged version of the Size Matters unit provides a one-day overview of nanoscience for teachers 
with very limited time. The goal of this lesson is to spark student's interest in nanoscience, introduce 
them to common terminology, and get them to start thinking about issues of size and scale. It includes a 
presentation and visual demonstrations, and recommends use of readings, worksheets, and diagrams from 
Size Matters Lesson 1. 

• The What's the Big Deal about Nanotechnology? PowerPoint introduces size and scale, applications 
of nanoscience, tools of the nanosciences, and unique properties at the nanoscale. 

• The mesogold and/or ferrofluid demonstrations visually illustrate how nanosized particles of a sub- 
stance exhibit different properties than larger sized particles of the same substance. 

• The Introduction to Nanoscience Student Reading and Worksheet (from Lesson 1) explains key 
concepts such as why nanoscience is different, why it is important, and how we are able to work at 
the nanoscale. 

• The Personal Touch Student Reading and Worksheet (from Lesson 1) focus on applications of nan- 
otechnology (actual and potential) set in the context of a futuristic story. They are designed to spark 
student's imaginations and get them to start generating questions about nanoscience. 

• The Scale Diagram (from Lesson 1) shows, for different size scales, the kinds of objects that are 
found, the tools needed to "see" them, the forces that are dominant, and the models used to explain 
phenomena. 

If you extend this lesson beyond one day, consider incorporating the following popular activities from 
Lessons 2 and 3: 

• The Number Line/Card Sort Activity (from Lesson 2) has students place objects along a scale and 
reflect on the size of common objects in relation to each other. 

• The Unique Properties Lab Activities (from Lesson 3) demonstrate specific aspects of size-dependent 
properties without using nanoparticles. 

www.ckl2.org 126 



Refer to the "Challenges and Opportunities" chart at the beginning of the unit before starting this lesson. 
Tell students that although making and using products at the nanoscale is not new, our focus on the 
nanoscale is new. We can gather data about nanosized materials for the first time because of the availability 
of new imaging and manipulation tools. You may not know all of the answers to the questions that students 
may ask. The value in studying nanoscience and nanotechnology is to learn how science understanding 
evolves and to learn science concepts. 

Essential Questions (EQ) 

What essential questions will guide this unit and focus teaching and learning? 

(Numbers correspond to learning goals overview document) 

1. How small is a nanometer, compared with a hair, a blood cell, a virus, or an atom? 

2. Why are properties of nanoscale objects sometimes different than those of the same materials at the 
bulk scale? 

4. How do we see and move things that are very small? 

6. What are some of the ways that the discovery of a new technology can impact our lives? 

Enduring Understandings (EU) 

Students will understand: 

(Numbers correspond to learning goals overview document) 

1. The study of unique phenomena at the nanoscale could change our understanding of matter and lead 
to new questions and answers in many areas, including health care, the environment, and technology. 

2. There are enormous scale differences in our universe, and at different scales, different forces dominate 
and different models better explain phenomena. 

3. Nanosized particles of any given substance exhibit different properties than larger particles of the 
same substance. 

4. New tools for seeing and manipulating increase our ability to investigate and innovate. 

Key Knowledge and Skills (KKS) 

Students will be able to: 

(Numbers correspond to learning goals overview document) 

1. Describe, using the conventional language of science, the size of a nanometer. Make size comparisons 
of nanosized objects with other small objects. 

3. Describe an application (or potential application) of nanoscience and its possible effects on society. 
Prerequisite Knowledge and Skills 

• Familiarity with atoms, molecules and cells. 

• Knowledge of basic units of the metric system and prefixes. 

Related Standards 

. NSES Science and Technology: 12EST2.1, 12EST2.2 
. NSES Science as Inquiry: 12ASI2.3 
. AAAS Benchmarks: 11D Scale #2 



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Table 1.21: 



Day 



Activity 



Time 



Materials 



Prior to this lesson 



Day 1 (50 min) 



Homework: (Optional) 30 min 
Reading & Worksheet: 
The Personal Touch 
(from Lesson 1) 

Homework: Reading 40 min 
& Worksheet: Intro- 
duction to Nanoscience 
(from Lesson 1) 

(Optional) Use The Per- 8 min 
sonal Touch story & 
worksheet as a basis for 
class discussion. Iden- 
tify and discuss some 
student questions from 
the worksheet. 

Show and pass around 2 min 
samples of mesogold 
and/or ferrofluid plus a 
strong magnet. 

Show the PowerPoint 25 min 
slides: What's the Big 
Deal about Nanotech- 
nology? Describe and 
discuss: 

• The term 
"nanoscience" 
and the unit 
"nanometer" 

• The tools of 
nanoscience 

• Examples of nan- 
otechnology 



Copies of The Personal 
Touch: Student Read- 
ing & Worksheet (from 
Lesson 1) 

Copies of Introduction 
to Nanoscience: Stu- 
dent Reading & Work- 
sheet (from Lesson 1) 
The Personal Touch: 
Student Reading & 
Worksheet (from Les- 
son 1) 



Mesogold 

Ferrofluid and a strong 

magnet 

What's the Big Deal 
about Nanotechnology? 
PowerPoint Slides & 
Teacher Notes 
Computer and projector 



Hand out Scale Dia- 5 min 
gram (from Lesson 1) 
and explain the impor- 
tant points represented 
on it. 

In pairs, have stu- 5 min 
dents review answers 
to the Introduction to 
NanoScience: Student 
Worksheet (from Lesson 

1) 



Copies of Scale Diagram 
(from Lesson 1) 



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128 



Table 1.21: (continued) 



Day Activity Time Materials 



Return to whole class 5 min 
discussion for questions 
and comments. 



Teacher Demonstration Instructions 

Overview 

Nanotechnology creates and uses structures that have novel properties because of their small size. The 
following two examples visually illustrate how nanosized particles of a given substance exhibit different 
properties than larger sized particles of the same substance. Paired with appropriate questions, these 
visual demonstrations can lead to stimulating discussion with your students. 

Mesogold 

Nanosized particles of gold — sometimes referred to as "mesogold" — exhibit different properties than bulk 
gold. For example, mesogold has a different melting point than bulk gold, and the color of mesogold can 
range from light red to purple depending on the size, shape, and concentration of the gold particles present. 

This difference in color has to do with the nature of interactions among the gold atoms and how they react 
to outside factors (like light) — interactions that average out in the large bulk material but not in the tiny 
nanosized particles. 

A number of organizations manufacture gold nanoparticles. Mesogold made by Purest Colloids, Inc., 
contains nanosized particles of gold suspended in water. At 10 parts per million (ppm) the liquid appears 
clear ruby red in color, illustrating how optical properties (color) of mesogold and bulk gold differ. 

The gold nanoparticles in Purest Colloid's mesogold are about 0.65 nanometers in diameter, and each 
particle consists of approximately 9 gold atoms. An atom of gold is about 0.25 nanometers in diameter, 
so the gold nanoparticles in Mesogold are only slightly larger than two times the diameter of a single 
gold atom. These particles stay suspended in deionized water, making it a true colloid. Other companies 
manufacture slightly larger mesogold particles, typically in the range of 70 - 90 nm. 

Gold nanoparticles are being investigated medical research for use in detecting and killing cancer cells 
and a variety of other applications. They are also advertised as mineral supplements, but without any 
accompanying scientific support of health benefits. 

More information on mesogold is available on the Purest Colloids website [1]. 

How to Use It as a Demonstration 

Show and pass around one or more samples of the mesogold. You may also want to show and pass around 
a piece of gold (e.g., a ring or gold foil) for comparison. 

Point out to your students how nanosized particles of a given substance (mesogold) exhibit different prop- 
erties (red color) than larger sized particles of the same substance (bulk gold that looks gold in color). 

Questions to stimulate classroom discussion: 

1. How do you know the bulk gold (e.g., ring or foil) is really made of gold atoms? 

Possible responses might include that it looks like gold, or because (in the case of a ring) jewelry is often 
made out of gold or may even have a stamp on it that "verifies" that it is made of gold. 

2. What could you do to determine that it is really made of gold atoms? 



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Figure 1.58: Mesogold colloidal gold from Purest Colloids, Inc. [1] 



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130 



You could test its physical properties — such as density, melting point, hardness (through a scratch test) — and 
compare these with the standard values for gold found in physical data charts. 

3. Is it possible that a standard microscope could help determine if it is real gold? 

No. Possible responses might include that a standard light microscope can only has resolution down to 
10~ 6 m, but we need to see down to the 1CT 9 m. 

4. How do you know the mesogold is really made of gold atoms? 

You could test its physical properties. Scientists use atomic emission spectrography to identify substances 
like mesogold by their spectral lines. 

5. Would the same criteria you used to determine if the bulk gold is really made of gold also work for 
determining if the mesogold is really made of gold? 

No, the criteria could differ, since nanoparticles exhibit different properties than bulk materials — and if 
you only have a few nanosized particles, some properties such as melting point and density may not even 
make sense. 

6. What other properties of mesogold might differ from bulk gold? 

Melting point and conductivity are examples of properties that might vary. 

Where to Buy It 

Mesogold can be ordered from http://www.purestcolloids.com/mesogold_price_list.htm or by call- 
ing 609-267-6284 from 9 am to 5 pm Eastern time. Prices range from around $30-\$70 per bottle, depend- 
ing on size (250 or 500 mL) and quantity ordered. One 250 mL bottle should be enough for demonstration 
purposes. 

Ferrofluid 

Ferrofluids contain nanoparticles of a magnetic solid, usually magnetite (Fe^O^), in a colloidal suspension. 
The nanoparticles are about 10 nm in diameter. Ferrofluids are interesting because they have the fluid 
properties of a liquid and the magnetic properties of a solid. For example, a magnet placed just below a 
dish or cell containing ferrofluid generates an array of spikes in the fluid that correspond to the magnetic 
lines of force. 




Figure 1.59: Ferrofluid from Educational Innovations, Inc. [2] 

When the magnet is removed, the spikes disappear. Ferrofluids were discovered by NASA when it was trying 
to control liquid in space. They have been used in many applications, including computers disk drives, 
low friction seals and loudspeakers. Medical researchers are even experimenting with using ferrofluids to 
deliver drugs to specific locations in the body by applying magnetic fields. 

More information about ferrofluids is available on the JChemEd web site [3] and the UW-Madison MRSEC 
web site [4] and [5] . 

131 www.ckl2.org 



How to Use It as a Demonstration 

Show and pass around one or more samples of ferrofluid along with a strong magnet. Let students play 
with the ferrofluid and magnet and see what they can make it do. You may also want to show and pass 
around another magnetic material, like a piece of iron, for comparison. Tell your students that since we 
have been able to make the particles in the ferrofluid so small, we have been able to change the physical 
state of the material from a solid to a liquid. 

Demonstrate that when you bring a magnet close to the liquid, you can see how the particles stream into a 
star, revealing lines of magnetic force. Point out that this example also illustrates how nanosized particles 
of a given substance (in this case, a solid called magnetite) exhibit different properties than larger sized 
particles of the same substance (even though bulk magnetite is a magnetic solid, it does not change visually 
like the fluid does when you bring a magnet close to it). 

Questions to stimulate discussion: 

1. What is a liquid? 

A liquid is a fluid that flows and takes the shape of its container. Fluids are divided into liquids and gases. 
In a liquid, the molecules are close together and have more freedom to move around than a solid but not 
as much as a gas. 

2. When you put the magnet near the ferrofluid, it distorts. What causes this distortion? 

The distortion is caused by the magnetic field of the magnet. The forces exerted by the magnetic field 
causes the particles of the ferrofluid (which are themselves like "mini-magnets") to line up in this pattern. 
Think about how two magnets have some orientations in relation to each other that they like more than 
others. 

3. What does this distortion represent? 

The lines you observe show the direction(s) in which the force field of the magnet acts at each point in 
space. 

4. Why does the solid magnetic material does not distort it's shape in the same way as the ferrofluid? 

The solid material does not distort because its particles are held more tightly (by attractive van der Waals 
forces, etc.) and thus must respond to the magnetic force as a group, not as individual particles. 

5. If the ferrofluid particles feel magnetic forces of attraction towards each other, why does the fluid not 
condense into a solid? 

The nanoparticles are coated with a stabilizing dispersing agent (surfactant) to prevent particle agglomer- 
ation even when a strong magnetic field is brought near the ferrofluid. The surfactant must overcome the 
attractive van der Waals and magnetic forces between the particles to keep them from clumping together. 

Where to Buy It 

Sealed display cells of ferrofluid can be ordered from Educational Innovations, Inc., at http://www. 
teachersource.com (click on "Browse or Search the Catalog", "Electricity! Magnetism! Engines!" and 
then "Ferrofluids") or call 1-888-912-7474. The Ferrofluid Preform Display Cell (item FF-200) is about $25 
and comes with a pair of circle magnets. A Ferrofluid Experiment Booklet is also available (item FF-150) 
for about $6. 

References 

• http : //www . purestcolloids . com/mesogold . htm 

• https://www.teachersource.com 

. http : // j chemed . chem . wise . edu/ JCESof t/CCA/CCA2/MAIN/FEFLUID/CD2Rl . HTM 

• http : //mrsec . wise . edu/Edetc/background/f errof luid/index . html 

www.ckl2.org 132 



• http://mrsec.wisc.edu/Edetc/IPSE/educators/activities/nanoMed.html 



What's the Big Deal about Nanotechnology? 




Science at the nanoscale involves a change of perspective! 
What is Nanoscale Science? 




Figure 1.60 



The study of objects and phenomena at a very small scale, roughly 1 to 100 nanometers (nm) 

— 10 hydrogen atoms lined up measure about 1 nm 

— A grain of sand is 1 million nm, or 1 millimeter, wide 

An emerging, interdisciplinary science involving 

— Physics 

— Chemistry 

— Biology 

— Engineering 

— Materials Science 

— Computer Science 



How Big is a Nanometer? 



133 



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Consider a human hand 




at :e : 



narsscale 



Figure 1.61 



Are You a Nanobit Curious? 



• What's interesting about the nanoscale? 

— Nanosized particles exhibit different properties than larger particles of the same substance 

• As we study phenomena at this scale we... 

— Learn more about the nature of matter 

— Develop new theories 

— Discover new questions and answers in many areas, including health care, energy, and technology 

— Figure out how to make new products and technologies that can improve people's lives 

Potential Impacts 

How might nanoscale science and engineering improve our lives? 
Innovations In Development or Under Investigation 



Health Care 

— Chemical and biological sensors, drugs and delivery devices, prosthetics and biosensors 
Technology 

— Better data storage and computation 
Environment 

— Clean energy, clean air 



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134 






Thin layers of gold are used Carbon nanotubes can be 
in tiny medical devices used for H fuel storage 



Possible entry point for 
nanomedical device 



Health Care: Nerve Tissue Talking to Computers 

• Neuro-electronic networks interface nerve cells with semiconductors 

— Possible applications in brain research, neurocomputation, prosthetics, biosensors 




Snail neuron grown on a chip 
that records the neuron's activity 

Figure 1.62 
Technology: A DVD That Could Hold a Million Movies 

• Current CD and DVD media have storage scale in micrometers 

• New nanomedia (made when gold self-assembles into strips on silicon) has a storage scale in nanome- 
ters 

— That is 1,000 times more storage along each dimension (length, width) or 1,000,000 times 

greater storage density in total! 

Technology: Building Smaller Devices and Chips 

• Nanolithography to create tiny patterns 

— Lay down "ink" atom by atom 



135 



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CD 




M i m 



DVB 






10 M«n 
Si (111) -Au 5x2 




10 \m 



1i nrr 



Figure 1.63 




mmhm \ 



ATM Tip 

^ ^ 1 fr> 






m 



....... 



.w 






*■• 



Mona Lisa, 8 microns tall, 
created byAFM nanolithography 



Transporting molecules to a surface 
by dip-pen nanolithography 



Figure 1.64 



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136 



Environment: Nano Solar Cells 

• Nano solar cells mixed in plastic could be painted on buses, roofs, and clothing 
— Solar becomes a cheap energy alternative! 

BwflgN 




::: in 



Fw. | .1* 

Nano solar cell: Inorganic nanorods embedded in semiconducting 
polymer, sandwiched between two electrodes 

Figure 1.65 

So How Did We Get Here? 

New Tools! As tools change, what we can see and do changes 
Using Light to See 

• The naked eye can see to about 20 microns 

— A human hair is about 50 - 100 microns thick 

• Light microscopes let us see to about 1 microns 

— Bounce light off of surfaces to create images 




Light microscope 
(magnification up to 1000x) 






to see red blood cells 
(400x) 




Figure 1.66 



Using Electrons to See 



Scanning electron microscopes (SEMs), invented in the 1930s, let us see objects as small as 10 nanometers 
— Bounce electrons off of surfaces to create images 



137 



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(4000x) 




Greater resolution to see things like blood cells in greater detail 



Figure 1.67 




This is about how big atoms are 
compared with the tip of the 
microscope 

Figure 1.68 



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138 



— Higher resolution due to small size of electrons 
Touching the Surface 

• Scanning probe microscopes, developed in the 1980s, give us a new way to "see" at the nanoscale 

• We can now image really small things, like atoms, and move them too! 

Size-Dependent Properties 

So now that we can "see" what's going on... 
Howdopropertieschangeatthenanoscale? 
Properties of a Material 

• A property describes how a material acts under certain conditions 

• Types of properties 

— Optical (e.g. color, transparency) 

— Electrical (e.g. conductivity) 

— Physical (e.g. hardness, melting point) 

— Chemical (e.g. reactivity, reaction rates) 

• Properties are usually measured by looking at large (~ 10 23 ) aggregations of atoms or molecules 
Optical Properties Change: Color of Gold 

• Bulk gold appears yellow in color 

• Nanosized gold appears red in color 

— The particles are so small that electrons are not free to move about as in bulk gold 

— Because this movement is restricted, the particles react differently with light 

Electrical Properties Change: Conductivity of Nanotubes 

• Nanotubes are long, thin cylinders of carbon 

— They are 100 times stronger than steel, very flexible, and have unique electrical properties 

• Their electrical properties change with diameter, "twist", and number of walls 

— They can be either conducting or semi-conducting in their electrical behavior 

Physical Properties Change: Melting Point of a Substance 

• Melting Point (Microscopic Definition) 

— Temperature at which the atoms, ions, or molecules in a substance have enough energy to 
overcome the intermolecular forces that hold the them in a "fixed" position in a solid 

— Surface atoms require less energy to move because they are in contact with fewer atoms of the 
substance 



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Figure 1.69 



V 




'Bulk" gold looks yellow 



12 nanometer gold "Bulk" gold 
looks yellow particles look red 



Figure 1.70 



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140 




Multi-walled 



Electric current 
varies by tube 
structure 




Zlg zag 



Armchair 



Ch.ial 



Figure 1.71 





In contact with 3 atoms 
In contact with 7 atoms 



Figure 1.72 



141 



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Table 1.22: Physical Properties Example: Substance's Melting Point II 



At the macroscale 



At the nanoscale 



The majority of the atoms are almost all on the inside of the ...split between the inside and the 

object surface of the object 





Changing an object's size. 



The melting point... 



...has a very small effect on the ...has a big effect on the percent- 
percentage of atoms on the sur- age of atoms on the surface 
face 
...doesn't depend on size ... is lower for smaller particles 



Size Dependant Properties 

Why do properties change? 
Scale Changes Everything 



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142 



♦ 



»- • 






1 



• There are enormous scale differences in our universe! 

• At different scales 

— Different forces dominate 

— Different models better explain phenomena 

• (See the Scale Diagram handout) 
Scale Changes Everything II 

• Four important ways in which nanoscale materials may differ from macroscale materials 

— Gravitational forces become negligible and electromagnetic forces dominate 

— Quantum mechanics is the model used to describe motion and energy instead of the classical 
mechanics model 

— Greater surface to volume ratios 

— Random molecular motion becomes more important 

Dominance of Electromagnetic Forces 



143 



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-:-■ 



Figure 1.73 



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144 



• Because the mass of nanoscale objects is so small, gravity becomes negligible 

— Gravitational force is a function of mass and distance and is weak between (low-mass) nanosized 
particles 

— Electromagnetic force is a function of charge and distance is not affected by mass, so it can be 
very strong even when we have nanosized particles 

— The electromagnetic force between two protons is 10 36 times stronger than the gravitational 
force! 

Quantum Effects 

• Classical mechanical models that we use to understand matter at the macroscale break down for... 

— The very small (nanoscale) 

— The very fast (near the speed of light) 

• Quantum mechanics better describes phenomena that classical physics cannot, like... 

— The colors of nanogold 

— The probability (instead of certainty) of where an electron will be found 

Surface to Volume Ratio Increases 

• As surface to volume ratio increases 

— A greater amount of a substance comes in contact with surrounding material 

— This results in better catalysts, since a greater proportion of the material is exposed for potential 
reaction 

Random Molecular Motion is Significant 

• Tiny particles (like dust) move about randomly 

— At the macroscale, we barely see movement, or why it moves 

— At the nanoscale, the particle is moving wildly, batted about by smaller particles 

• Analogy 

— Imagine a huge (10 meter) balloon being batted about by the crowd in a stadium. From an 
airplane, you barely see movement or people hitting it; close up you see the balloon moving 
wildly. 

Nanotechnology is a Frontier in Modern-Day Science 

What else could we possibly develop? 

What other things are nanoengineers, researchers and scientists investigating? 

Detecting Diseases Earlier 

• Quantum dots glow in UV light 

— Injected in mice, collect in tumors 

— Could locate as few as 10 to 100 cancer cells 

Growing Tissue to Repair Hearts 

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* 



* 







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Macrogold 




NanogoM 




■ ■ ■ ■ 




Figure 1.74 



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Arta-ft*1r* 7 -tv* *Jt« - t i flO**** - Um 





«.Wk^-»b' 



Figure 1.75 



147 



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Figure 1.76 




Quantum Dots: Nanometer-sized crystals 
that contain free electrons and emit 
photons when submitted to UV light 




Early tumor detection, 
studied in mice 



Figure 1.77 



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148 




Cardiac tissue grown with the help 
of nanofiber filaments 

Figure 1.78 

• Growing cardiac muscle tissue is an area of current research 

— Grown in the lab now, but the fibers grow in random directions 

— With the help of nanofiber filaments, it grows in an orderly way 

• Could be used to replace worn out or damaged heart tissue 
Preventing Viruses from Infecting Us 

• The proteins on viruses bind to our body cells 

• Could cover these proteins with nanocoatings 

— Stop them from recognizing and binding to our cells 

— We would never get the flu! 

• A protein recognition system has been developed 
Making Repairs to the Body 

• Nanorobots are imaginary, but nanosized delivery systems could... 

— Break apart kidney stones, clear plaque from blood vessels, ferry drugs to tumor cells 

Pause to Consider 

How delicate are nanoscale - sized objects? 

How well do we understand the environmental and health impacts of nanosized clusters of particles? 

Nanodevices Are Sensitive! 

• Radiation particles can cause fatal defects during manufacturing 

— Development requires very clean environments 

— Only a few, out of many produced, are perfect 

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Gold tethered to the 
protein shell of a virus 




Influenza virus: Note proteins 
on outside that bind to cells 



Figure 1.79 



Potential Risks of Nanotechnology 



Health issues 

— Nanoparticles could be inhaled, swallowed, absorbed through skin, or deliberately injected 

— Could they trigger inflammation and weaken the immune system? Could they interfere with 
regulatory mechanisms of enzymes and proteins? 

Environmental issues 

— Nanoparticles could accumulate in soil, water, plants; traditional filters are too big to catch 
them 

New risk assessment methods are needed 

— National and international agencies are beginning to study the risk; results will lead to new 
regulations 



Summary: Science at the Nanoscale 



An emerging, interdisciplinary science 



Nanotechnology: A New Day 



The nanotechnology revolution will lead to... 

— New areas of research and technology design 

— Better understanding of matter and interactions 

— New ways to tackle important problems in healthcare, energy, the environment, and technology 



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150 




Figure 1.80 



151 



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Pit created by nuclear radiation 

(an alpha particle) hitting a mica surface 

Figure 1.81 



Materials Science 




fWts 

Biology 




Chemistry 

Engii ering 



Figure 1.82 



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152 




Figure 1.83 



153 



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Teacher Notes 

Overview 

These slides introduce students to what nanoscience is, and capture in a relatively brief overview what is 
interesting about science at the nanoscale. We want students to see that science is a dynamic, exciting, 
and evolving undertaking that impacts the world around us through the technological development that 
accompanies the progress in scientific understanding and tool development. 

In contrast to the other lessons in the Size Matters unit that focus primarily (and more deeply) on one 
aspect of nanoscience, this one-day overview surveys all of the topics addressed by the other Size Matters 
lessons. Questions such as "How big is a nanometer" and "What are the various types of microscopes used 
to see small things" are addressed. Properties of materials that can vary at the nanoscale are identified, 
and some fundamental differences between the nanoscale and bulk scale are highlighted. Finally, examples 
of currently existing commercial applications, areas of research, and visions for the future are presented. 
A final slide summarizes key points about nanoscience as an emerging, interdisciplinary science. 

Slide 1: What's the Big Deal about Nanoscience? 

Explain to students that you're going to explain what nanoscience is and how we see small things, and 
give a few examples of interesting structures and properties of the nanoscale. 

Slide 2: What is Nanoscale Science? 

Nanoscale science deals with the study of phenomena at a very small scale — 10~ 7 m(100 nm) to 1CT 9 m(l nm) — where 
properties of matter differ significantly from those at larger scales. This very small scale is difficult for 
people to visualize. There are several size- and scale-related activities as part of the NanoSense materials 
that you can incorporate into your curriculum that help students think about the nanoscale. 

This slide also highlights that nanoscale science is a multidisciplinary field and draws on areas outside 
of chemistry, such as biology, physics, engineering and computer science. Because of its multidisciplinary 
nature, nanoscience may require us to draw on knowledge in potentially unfamiliar academic fields. 

Slide 3: How Big is a Nanometer? 

This slide gives a "powers of ten" sense of scale. If you are running the slides as a PowerPoint presentation 
that is projected to the class, you could also pull up one or more powers of ten animations. See http: 
//micro. magnet .fsu.edu/primer/java/scienceopticsu/powersof 10 for a nice example that can give 
students a better sense of small scale. 

As you step through the different levels shown in the slide, you can point out that you can see down to 
about #3 (1000 microns) with the naked eye, and that a typical microscope as used in biology class will get 
you down to about #5 (10 microns). More advanced microscopes, such as scanning electron microscopes 
can get you pretty good resolution in the #6 (1 micron) range. Newer technologies (within the last 20 
years or so) allow us to "see" in the #7 (100 nanometer) through #9 (1 nanometer) ranges. These are the 
scanning probe and atomic force microscopes. 

Slide 4: Are you a Nanobit Curious? 

This slide highlights why we should care about nanoscience: It will change our lives and change our 
understanding of matter. A group of leading scientists gathered by the National Science Foundation in 
1999 said: "The effect of nanotechnology on the health, wealth and standard of living for people in this 
century could be at least as significant as the combined influences of microelectronics, medical imaging, 
computer-aided engineering and manmade polymers developed in the past century." (Accessed August, 
2005, from http : //www . techbizf 1 . com/news_desc . asp?art icle_id=1792 . ) 

Slide 5: Potential Impacts 

The next few slides provide examples of how nanoscale science and engineering might improve our lives. 

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Slide 6: Innovations In Development or Under Investigation 

Point out that tools for manipulating materials are becoming more sophisticated and improving our un- 
derstanding of how atoms and molecules can be controlled. This will lead to significant improvements in 
materials, and, in turn, to new products, applications, and markets that could have revolutionary impact 
on our lives. 

This next few slides focus on innovations related to the environment, technology, and healthcare. A few of 
these products being commercialized now, but most are in research labs or are envisioned for the distant 
future. 

Slide 7: Health Care: Nerve Tissue Talking to Computers 

Researchers are studying the electrical interfacing of semiconductors with living cells — in particular, neu- 
rons — to build hybrid neuro-electronic networks. Cellular processes are coupled to microelectronic devices 
through the direct contact of cell membranes and semiconductor chips. For example, electrical interfacing 
of individual nerve cells and semiconductor microstructures allow nerve tissue to directly communicate their 
impulses to computer chips. Pictured is a snail neuron grown on a CMOS chip with 128 x 128 transistors. 
The electrical activity of the neuron is recorded by the chip, which is fabricated by Infineon Technologies. 
This research is directed (1) to reveal the structure and dynamics of the cell-semiconductor interface and 
(2) to build up hybrid neuro-electronic networks. Such research explores the new world at the interface of 
the electronics in inorganic solids and the ionics in living cells, providing the basis for future applications 
in medical prosthetics, biosensorics, brain research and neurocomputation. 

References: 

• Nanopicture of the day from Peter Fromherz: http : //www . nanopicof theday . org/2003Pics/Neuroelectronic' 
20Interf ace . htm 

• Max Planck research: http://www.biochem.mpg.de/mnphys/ 

Slide 8: Technology: A DVD That Could Hold a Million Movies 

In 1959, Richard Feynman asked if we could ever shrink devices down to the atomic level. He couldn't 
find any laws of physics against it. He calculated that we could fit all printed information collected over 
the past several centuries in a 3 - dimensional cube smaller than the head of a pin. How far have we 
come? A 2 - dimensional version of Feynman 's vision is in research labs. The picture on this slide 
illustrates the potential of nano-devices for data storage. On the left are images of two familiar data 
storage media: the CD-ROM and the DVD. On the right is a self-assembled memory on a silicon surface, 
formed by depositing a small amount of gold on it. It looks like CD media, except that the length scale 
is in nanometers, not micrometers. So the corresponding storage density is a million times higher! The 
surface automatically formats itself into atomically-perfect stripes (red) with extra atoms on top (white). 
These atoms are neatly lined up at well-defined sites along the stripes, but occupy only about half of them. 
It is theoretically possible to use the presence of an atom to store a 1, and the absence to store a 0. The 
ultimate goal would be to build a data storage medium that needs only a single atom per bit. The big 
question is how to write and read such bits efficiently. 

References: 

• Franz J. Himpsel's web site: http://uw.physics.wisc.edu/-himpsel/nano.html 

• R. Bennewitz et al., "Atomic scale memory at a silicon surface" Nanotechnology 13, 499 (2002) 

Slide 9: Technology: Building Smaller Devices and Chips 

A technique called nanolithography lets us create much smaller devices than current approaches. For 
example, the Atomic Force Microscope (AFM) nanolithography image of the Mona Lisa was created by a 

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probe oxidation technique. This technique can be used to further miniaturize the electrical components 
of microchips. Dip pen nanolithography is a 'direct write' technique that uses an AFM to create patterns 
and to duplicate images. "Ink" is laid down atom by atom on a surface, through a solvent — often water. 

References: 

• AFM Oxidation nanolithography Principles/Lithographies/AFM_Oxidation_Lithography_mode37.html 
http : //www . ntmdt . ru/SPMTechniques/ Principles/Lithographies/AFM_Oxidation_Lithography_- 
mode37.html 

• Dip pen nanolithography: http://www.chem.northwestern.edu/~mkngrp/dpn.htm 

Slide 10: Environment: Nano Solar Cells 

Enough energy from the sun hits the earth every day to completely meet all energy needs on the planet, 
if only it could be harnessed. Doing so could wean us off of fossil fuels like oil and provide a clean 
energy alternative. But currently, solar-power technologies cost as much as 10 times the price of fossil fuel 
generation. Chemists at U.C. Berkeley are developing nanotechnology to produce a photovoltaic material 
that can be spread like plastic wrap or paint. These nano solar cells could be integrated with other building 
materials, and offer the promise of cheap production costs that could finally make solar power a widely 
used electricity alternative. 

Current approaches embed nanorods (bar-shaped semiconducting inorganic crystals) in a thin sheet (200 nanometers 
deep) of electrically conductive polymer. Thin layers of an electrode sandwich these nanorod-polymer com- 
posite sheets. When sunlight hits the sheets, they absorb photons, exciting electrons in the polymer and 
the nanorods, which make up 90 percent of the composite. The result is a useful current that is carried 
away by the electrodes. Eventually, nanorod solar cells could be rolled out, ink-jet printed, or even painted 
onto surfaces, so that even a billboard on a bus could be a solar collector. 

References: 

• Painting on solar cells: http: //www. calif orniasolarcenter. org/solareclips/2003. 01/20030128-6. 
html 

• Cheap, plastic solar cells may be on the horizon: http : //www . berkeley . edu/news/media/releases/ 
2002/03/28_solar . html 

• New nano solar cells to power portable electronics: http://www.californiasolarcenter.org/ 
solareclips/2002 . 04/20020416-7 . html 

Slide 11: So How Did We Get Here? 

This slide denotes the beginning of a short discussion of the evolution of imaging tools (i.e. microscopes). 
One of the big ideas in science is that the creation of tools or instruments that improve our ability to 
collect data is often accompanied by new science understandings. Science is dynamic. Innovation in 
scientific instruments is followed by a better understanding of science and is associated with creating 
innovative technological applications. 

Slide 12: Using Light to See 

You may want to point out that traditional light microscopes are still very useful in many biology-related 
applications since things like cells and some of their features can readily be seen with this tool. They are 
also inexpensive relative to other microscopes and are easy to set up. 

Slide 13: Using Electrons to See 

Point out that the difference between the standard light microscope and the scanning electron microscope 
is that electrons, instead of various wavelengths of light, are "bounced" off the surface of the object being 

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viewed, and that electrons allow for a higher resolution because of their small size. You can use the analogy 
of bouncing bb's on a surface to find out if it is uneven (bb's scattering in all different directions) compared 
to using beach balls to do the same job. 

Slide 14: Touching the Surface 

Point out how small the tip of the probe is compared to the size of the atoms in the picture. Point out 
that this is one of the smallest tips you can possibly make, and that it has to be made from atoms. Also 
point out that the tip interacts with the surface of the material you want to look at, so the smaller the 
tip, the better the resolution. But because the tip is made from atoms, it can't be smaller than the atoms 
you are looking at. Tips are made from a variety of materials, such as silicon, tungsten, and even carbon 
nanotubes. 

The different types of scanning probe microscopes are discussed in Lesson 4: Tools of the Nanosciences. 
For example, in the STM, a metallic tip interacts with a conducting substrate through a tunneling current 
(STM). With the AFM, the van der Waals force between the tip and the surface is the interaction that is 
traced. 

Slide 15: Size-Dependent Properties 

The next few slides focus on how nanosized materials exhibit some size-dependent effects that are not 
observed in bulk materials. 

Slide 16: Properties of a Material 

It is important to talk with your students about how we know about the properties of materials — how are 
they measured and on what sized particles are the measurements made? In most cases, measurements are 
made on macroscale particles, so we tend to have good information on bulk properties of materials but not 
the properties of nanoscale materials (which may be different). 

This slide also points out four types of properties that are often affected by size. This is not an exhaustive 
list but rather a list of important properties that usually come up when talking about nanoscience. 

[Note: This slide summarizes the content in the "What Does it Mean to Talk About the Characteristics and 
Properties of a Substance?" and "How Do We Know the Characteristics and Properties of Substances?" 
paragraphs in the Size-Dependant Properties student reading.] 

Slide 17: Optical Properties Change: Color of Gold 

The gold example illustrates a simple comparison between the nano and bulk properties of a particular 
material. It is important to point out to your students that we can't say exactly what color a material 
will always be at a given particle size. This is because there are other factors involved like arrangement 
of atoms and molecules in the particles and the charge(s) present on particles. However, it is possible to 
control for these various factors to create desired effects, as in this case the creation of "red" gold using 12 
nanometer-sized particles. 

[Note: This slide summarizes the content in the "What's Different at the Nanoscale" paragraph in the 
Size-Dependant Properties student reading.] 

Slide 18: Electrical Properties Example: Conductivity of Nanotubes 

Electrical properties of materials are based on the movement of electrons and the positively-charged spaces, 
or "holes," they leave behind. The electronic properties of a nanotube depend on the direction in which 
the sheet was rolled up. Some nanotubes are metals with high electrical conductivity, while others are 
semiconductors with relatively large band gaps. Which one it becomes depends on way that it is rolled 
(also called the "chirality" of the nanotube"). If it's rolled so that its hexagons line up straight along the 
tube's axis, the nanotube acts as a metal. If it's rolled on the diagonal, so the hexagons spiral along the 
axis, it acts as a semiconductor. See the "Unique Properties at the Nanoscale: Teacher Reading" for more 
information. 

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Slide 19: Physical Properties Change: Melting Point of a Substance 

Note that even in a solid, the atoms are not really "fixed" in place but are rather vibrating or rotating 
around a fixed point. In liquids, the atoms also rotate and move past each other in space (translational 
motion), although they don't have enough energy to completely overcome the intermolecular forces and 
move apart as in a gas. 

Slide 20: Physical Properties Example: Melting Point of a Substance II 

At the nanoscale, a smaller object will have a significantly greater percentage of its atoms on the surface 
of the object. Since surface atoms need less energy to move (because they are in contact with fewer atoms 
of the same substance), the total energy needed to overcome the intermolecular forces hold them "fixed" 
is less and thus the melting point is lower. 

Slide 21: Size-Dependant Properties 

The next few slides focus on why nanosized materials exhibit size-dependent effects that are not observed 
in bulk materials. 

Slide 22: Scale Changes Everything 

Ask your students to refer to the Scale Diagram handout. Use the diagram to point out how there are 
enormous scale differences in the universe (left part of the diagram), and where different forces dominate 
and different models better explain phenomena (right part of diagram). Scale differences are also explored 
in more detail in "Visualizing the Nanoscale: Student Reading" from Lesson 2: Size and Scale. 

Slide 23: Scale Changes Everything II 

This slide highlights four ways in which nanoscale materials may differ from their macroscale counterparts. 
It is important to emphasize that just because you have a small group of some type of particle, it does 
not necessarily mean that a whole new set of properties will arise. Whether or not different observable 
properties arise depends not only on aggregation, but also on the arrangement of the particles, how they 
are bonded together, etc. This slide sets up the next four slides, where each of the four points (gravity, 
quantum mechanics, surface to volume ratio, random motion) is described in more detail. 

Slide 24: Dominance of Electromagnetic Forces 

This slide compares the relative strength between the electromagnetic and gravitational forces. The grav- 
itational force between two electrons is feeble compared to the electromagnetic forces. The reason that 
you feel the force of gravity, even though it is so weak, is that every atom in the Earth is attracting 
every one of your atoms and there are a lot of atoms in both you and the Earth. The reason you aren't 
bounced around by electromagnetic forces is that you have almost the same number of positive charges as 
negative ones, so you are (essentially) electrically neutral. Gravity is only (as far as we know) attractive. 
Electromagnetic forces (which include electrical and magnetic forces) can be either attractive or repul- 
sive. Attractive and repulsive forces cancel each other out; they neutralize each other. Since gravity has 
no repulsive force, there's no weakening by neutralization. So even though gravity is much weaker than 
electrical force, gravitational forces always add to each other; they never cancel out. 

Slide 25: Quantum Effects 

This slide highlights that, at the nanoscale, we need to use quantum mechanics to describe behavior rather 
than classical mechanics. The properties reading describe the differences. You can decide how much 
discussion to have about classical and quantum mechanics with your students. For the purposes of this 
introductory unit, it is important to let students know that we use a different set of "rules" to describe 
particles that fall into the nanoscale and smaller range. 

Slide 26: Surface to Volume Ratio Increases 

This slide highlights the fact that as you decrease particle size, the amount of surface area increases. The 

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three-part graphic on the slide illustrates how, for the same volume, you can increase surface area simply 
by cutting. Each of the three blocks has the same total volume, but the block that has the most cuts has 
a far greater amount of surfaces area. This is an important concept since it effects how well a material 
can interact with other things around it. With your students, you can use following example. Which will 
cool a glass of water faster: Two ice cubes, or the same two ice cubes (same volume of ice) that have been 
crushed? 

Slide 27: Random Molecular Motion is Significant 

This slide highlights the importance of random ("Brownian") motion at small scales. Tiny particles, 
such as dust, are in a constant state of motion when seen through microscope because they are being 
batted about by collisions with small molecules. These small molecules are in constant random motion 
due to their kinetic energy, and they bounce the larger particle around. At the macroscale, random 
motion is much smaller than the size of the particle, but at the nanoscale this motion is large when 
compared to the size of the particle. A nice animation that illustrates this concept is available at http : 
//galileo . phys . Virginia . edu/classes/109N/more_stuff /Applet s/brownian/brownian . html 

Slide 28: Nanotechnology is a Frontier of Modern-Day Science 

The next few slides focus on some cutting-edge research and applications that nanoscientists and engineers 
are working on. 

Slide 29: Detecting Diseases Earlier 

Quantum dots are small devices that contain a tiny droplet of free electrons, and emit photons when 
submitted to ultraviolet (UV) light. Quantum dots are considered to have greater flexibility than other 
fluorescent materials, which makes them suited for use in building nanoscale applications where light is 
used to process information. Quantum dots can, for example, be made from semiconductor crystals of 
cadmium selenide encased in a zinc sulfide shell as small as 1 nanometer (one-billionth of a meter). In UV 
light, each dot radiates a brilliant color. 

Because exposure to cadmium could be hazardous, quantum dots have not found their way into clinical 
use. But they have been used as markers to tag particles of interest in the laboratory. Scientists at 
Georgia Institute of Technology have developed a new design that protects the body from exposure to 
the cadmium by sealing quantum dots in a polymer capsule. The surface of each capsule can attach to 
different molecules. In this case, they attached monoclonal antibodies directed against prostate-specific 
surface antigen, which is found on prostate cancer cells. The researchers injected these quantum dots into 
live mice that had human prostate cancers. The dots collected in the tumors in numbers large enough to 
be visible in ultraviolet light under a microscope. Because the dots are so small, they can be used to locate 
individual molecules, making them extremely sensitive as detectors. Quantum dots could improve tumor 
imaging sensitivity tenfold with the ability to locate as few as 10 to 100 cancer cells. Using this technology, 
we could detect cancer much earlier, which means more successful, easier treatment. 

References: 

• Quantum dots introduction: http://vortex.tn.tudelft.nl/grkouwen/qdotsite.html 

• Lawrence Livermore Labs work in quantum dots: http://www.llnl.gov/str/Lee.html 

• Quantum dots light up prostate cancer: http://www.whitaker.org/news/nie2.html 

Slide 30: Growing Tissue to Repair Hearts 

Cardiac muscle tissue can be grown in the lab, but the fibers grow in random directions. Researchers at 
the University of Washington are investigating what type of spatial cues they might give heart-muscle cells 
so that they order themselves into something like the original heart-muscle tissue. Working with one type 
of heart muscle cell, they have been able to build a two-dimensional structure that resembles native tissue. 

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They use nanofibers to "instruct" muscle cells to orient themselves in a certain way. They have even able 
to build a tissue-like structure in which cells pulse or 'beat' similar to a living heart. 

This image on this slide shows cardiac tissue grown with the aid of nanofiber filaments. It displays well- 
organized growth that is potentially usable to replace worn out or damaged heart tissue. The ultimate 
goal of building new heart-muscle tissue to repair and restore a damaged human heart is a long way off, 
but there have been big advances in tissue engineering in recent years. 

References: 

• University of Washington cardiac muscle work: http : //www . Washington . edu/admin/f inmgmt/annrpt/ 
mcdevitt .htm 

Slide 31: Preventing Viruses from Infecting Us 

If we could cover the proteins that exist on the influenza virus, we could prevent the virus from recognizing 
and binding to our body cells. We would never get the flu! A protein recognition system has already been 
developed. More generally, this work suggests that assembled virus particles can be treated as chemically 
reactive surfaces that are potentially available to a broad range of organic and inorganic modification. 

References 

• Virus nanoblocks: http://pubs.acs.org/cen/topstory/8005/8005notw2.html 

Slide 32: Making Repairs to the Body 

The image on this slide depicts what one nanoscientist from the Foresight Institute imagines might be 
possible one day in the far future. It shows how a nanorobot could potentially interact with human cells. 
When people hear of nanotechnology from science fiction, this is often the form that it takes. But we do 
not know if such a probe is possible. Nanobots like this, if even possible, are probably decades away. What 
are currently being researched, with hopeful outcomes, are nanosized drug delivery systems that could be 
used to diagnose disease and fight pathogens. 

The fantasy nanobot, for example, could (1) be used to cure skin diseases (embedded in a cream, they 
could remove dead skin and excess oils, apply missing oils), (2) be added to mouthwash to destroy bacteria 
and lift plaque or tartar from the teeth to be rinsed away, (3) augment the immune system by finding and 
disabling unwanted bacteria and viruses, or (4) nibble away at plaque deposits in blood vessels, widening 
them to prevent heart attacks. 

References: 

• Nanorobots: medicine of the future: http://www.ewh.ieee.org/rl0/bombay/news3/page4.html 

• Robots in the body: http://www.genomenewsnetwork.org/articles/2004/08/19/nanorobots. 
php 

• Drexler and Smalley make the case for and against molecular assemblers http://pubs.acs.org/ 
cen/coverstory/8 148/8 148counterpoint .html 

Slide 33: Pause to Consider 

The next two slides focus on the delicate nature of nanosized objects, the potential risks of nanotechnology 
to humans and the environment, and the need study the risks and regulate the development of products 
that contain nanoparticles. 

Slide 34: Nanodevices are Sensitive 
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Because of their small size, nanodevices are very sensitive and can easily be damaged by, for example, 
the natural environmental radiation all around us. In the picture for this example, we see a pit caused 
by an alpha particle hitting the surface of mica. An alpha particle is a high-energy helium nucleus that 
is the lowest-energy form of nuclear radiation. Alpha particles are also the particles that Rutherford 
used for the gold foil experiment in which he discovered the arrangement of protons within the atom 
that is now commonly known as the nucleus. The impact of alpha particles on a solid surface can cause 
physical damage by causing other atoms in the surface to be moved out of place. These types of defects 
can be potentially fatal in high-density electronics and nanodevices. To compensate, extremely clean 
manufacturing environments and very high redundancy — perhaps millions of copies of nanodevices for a 
given application — are required. 

References: 

• Fei and Fraundorf on Alpha recoil pits: http://www.nanopicoftheday.org/2004Pics/February2004/ 
AlphaRecoil.htm 

• Nano memory scheme handles defects: http : //www . trnmag . com/Stories/2004/090804/Nano_memory_ 
scheme_handles_def ects_Brief _090804 . html 

Slide 35: Potential Risks of Nanotechnology 

Nanotechnology's potential is encouraging, but the health and safety risks of nanoparticles have not been 
fully explored. We must weigh the opportunities and risks of nanotechnology in products and applications 
to human health and the environment. Substances that are harmless in bulk could assume hazardous 
characteristics because when particles decrease in size, they become more reactive. A growing number of 
workers are exposed to nanoparticles in the workplace, and there is a danger that the growth of nanotech- 
nology could outpace the development of appropriate safety precautions. Consumers have little knowledge 
of nanotechnology, but worries are already beginning to spread. For example, environmental groups have 
petitioned the Food and Drug Administration to pull sunscreens from the market that have nano-size tita- 
nium dioxide and zinc oxide particles. As nanotechnology continues to emerge, regulatory agencies must 
develop standards and guidelines to reduce the health and safety risks of occupational and environmental 
nanoparticle exposure. 

References: 

• Risks of nanotechnology: http://en.wikipedia.org/wiki/Nanotechnology 

• Overview of nanotechnology: Risks, initiatives, and standardization: http://www.asse.org/nantechArticle. 
htm 

Slides 36: Summary: Science at the Nanoscale 

Nanoscience is truly an interdisciplinary science. Progress in nanoscale science and technology results from 
research involving various combinations of biology, chemistry, physics, materials engineering, earth science, 
and computer science. Nanoscience also provides a way to revisit the core concepts from these domains 
and view them through a different lens. Learning about nanoscience can support understanding of the 
interconnections between the traditional scientific domains and provide compelling, realworld examples of 
science in action. 

Engineering is a discipline rarely discussed in science. Yet, engineering and design are the disciplines that 
accompany, and sometimes precede, new findings in science. The focus on nanotechnology highlights the 
intimate nature of the pairing of science and engineering to produce products for society. 

Slides 37: Nanotechnology: A New Day 

Nanoscience is an emerging science that will change our understanding of matter and help us solve hard 
problems in many areas, including energy, health care, the environment, and technology. With the power 

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to collect data and to manipulate particles at such a tiny scale, new areas of research and technology design 
are emerging. Some applications — like stain resistant pants and nanopaint on cars — are here today, but 
most applications are years or decades away. But nanoscience gives us the potential to understand and 
manipulate matter more than ever before. 



Image Sources 



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http : //www . weizmann . ac . il/chemphys/kral/nano2 . jpg. 

http : //www . ap . stmarys . ca/demos/content/thermodynamics/brownian_motion/rand_path .gif . 

http : //www. cs .utexas .edu/users/s2s/lat est /bi alt 1/src/WhatIsNano/ images/molecule .gif . 

http : //www. chem . northwest em . edu/~mkngrp/dpn . htm. 

http : //www . uwgb . edu/dutchs/GRAPHICO/GEOMORPH/Surf aceVolO . gif. 

http : //www . Washington . edu/admin/f inmgmt/annrpt/mcdevitt . htm. 

http : //digilander . libero . it/geodesic/buckyball-2Layerl .jpg. 

http : //www . hyperorg . com/blogger/images/sunrise_mediuml .jpg. 

Tip and surface and electron tunneling [If. 

http : //www . iap . tuwien . ac . at /www/surf ace/STM_Gallery/stm_animated .gif. 

http : //www . biochem . mpg . de/mnphys/publicat ions/05voef ro/abstract . html. 

http : //www. cs .utexas .edu/users/s2s/lat est /bi alt 1/src/WhatIsNano/ images/molecule .gif . 

http : //www . genomenewsnetwork . org/articles/2004/08/19/nanorobots . php. 

http : //www . uwgb . edu/dutchs/GRAPHICO/GEOMDRPH/Surf aceVolO . gif. 

http : //www . berkeley . edu/news/media/releases/2002/03/28_solar . html. 

http : //www . supanet . com/motoring/testdrives/news/40923/. 

How the AFM works [7j. 

http: //www. library .utoronto. ca/engineering-computer-science/news_bulletin/images/ 
nanotube. jpeg. 



(19 
(20 
(21 
(22 
(23 
(24 
(25 

www.ckl2.org 162 



http : //mechmat . caltech . edu/~kaushik/park/3-3-0 . htm. 
A severely distorted nanotube still doesn't break [3].. 
http : //www. whitaker. org/news/nie2. html. 
Laser used to measure cantilever movement [5]. 
Zoom in of tip [3j. 



(26) http ://pubs . acs . org/cen/topstory/8005/8005notw2. html. 

(27) . 

(28) http: //sere, carleton. edu/usingdata/nasaimages/index^.html. 

(29) http : //www . berkeley . edu/news/media/releases/2002/03/28_solar . html. 

(30) . 

(31) http : //www . genomenewsnetwork . org/articles/2004/08/19/nanorobots . php. 

(32) http : //www. physics . umd. edu/lecdem/outreach/QOTW/pics/k3-06 . gif. 

(33) http : //www. mater ialsworld.net/nclt/docs/Introduction /o20to / 20Nano / 20 l-18-05.pdf. 

(34) http : //www . ap . stmarys . ca/demos/content/thermodynamics/brownian_motion/rand_path .gif . 

(35) http : //physchem . ox . ac . uk/~rgc/research/af m/af ml . htm. 

(36) Scientific American. . 

(37) http : //www . uwgb . edu/dutchs/GRAPHICO/GEDMORPH/Surf aceVolO . gif. 

(38) http: //www. antonine- education. co .uk/Phy sics_AS/Module_l/Topic_5/em_ force. jpg. 

(39) http : //www . nanoscience . com/educat ion/AFM . html. 

(40) http : //news . bbc.co . uk/ olmedia/760000/ images /_762 l .022_red_blood_cells300. jpg. 

(41) Scientific American. . 

(42) http : //mrsec . wise . edu/Edetc/modules/MiddleSchool/SPM/MappingtheUnknown . pdf . 

(43) http : //www. nanoptek. com/digitalptm. html. 

(44) . 

(45) http :/ /www . trnmag . com/Stories/200J i ./09080J l ./Nano_memory_scheme_handles_defects_Brief_ 
090804.html. 

(46) powders. com/images/zno/im_zinc_oxide_particles.jpg 

http : //www. abc.net. au/science/news/stories/sll65709.htm 
http: //www. J^girls .gov/body/ sunscreen, jpg. 

(47) http: //www. antonine- education. co . uk/Phy si cs_AS/Module_l /Topi c_ 5/ em_ force. jpg. 

(48) An STM tip. 

(49) http://www.nbi. dk/ -pmhansen/ gold_trap .ht 

http : //www. sharps- jewellers . co . uk/rings/images/bien-hccncsq5 . jpg. 

(50) http://www.almaden.ibm.com. 

(51) http: 

//iuiuiu. zephyr, dti.ne. jp/~john8tam/main/Library/influenza_site/influenza_virus. jpg. 

(52) Wood AFM model. 

(53) http : //www. foresight . org/Conferences/MNT7/Abstracts/Levi/. 

163 www.ckl2.org 



(54 
(55 
(56 
(57 
(58 
(59 

(60 

(61 

(62 
(63 
(64 
(65 
(66 
(67 
(68 
(69 
(70 
(71 
(72 
(73 
(74 
(75 
(76 
(77 

(78 
(79 
(80 
(81 
(82 
(83 



http : //www . almaden . ibm . com/vis/stm/atomo . html, 
http : //uw . physics . wise . edu/~himpsel/nano . html. 

http : //mechmat . caltech . edu/~kaushik/park/3-3-0 . htm. 

. biotech. iastate. edu/ facilities/BMF /images/ SEMFayel.jpg 
http ://cgee. hamline. edu/ see/ 'quest ions/ 'dp _cycles/cycles_bloodcells_bw. jpg. 

http : //news . bbc.co . uk/ olmedia/760000/ images /_764022_red_blood_cells300. jpg. 

http : //www. nbi . dk/~pmhansen/gold_ trap . ht 
http: //www. sharps- jewellers . co . uk/rings/images/bien-hccncsq5 . jpg. 

http : //www. materialsworld.net/nclt/docs/Introduction /o20to /o20Nano / 201- 18-05.pdf. 

http : //www . Washington . edu/admin/f inmgmt/annrpt/mcdevitt . htm. 

http : //www . chemistry . nmsu . edu/~etrnsf er/nanowires/. 

http ://english. east day . com/east day /englishedit ion/metro/user object lai710823.html. 
http : //uw . physics . wise . edu/~himpsel/nano . html. 

http: //www. whitaker. org/news/nie2. html. 

http ://cgee. hamline. edu/ see/ quest ions/dp _cycles/cycles_bloodcells_bw. jpg. 

http: //pubs, acs . org/cen/topstory/8005/8005notw2. html. 
http : //www . biochem . mpg . de/mnphys/publicat ions/05voef ro/abstract . html. 

http : //www. asylumresearch. com/ImageGallery /Mat/Mat . shtml#M7. 

http://rn.rsec. wise. edu/Edetc/IPSE/ 'educators/ 'activities/nanoTex. html. 

http : //www . nano . uts . edu . au/pics/au_atoms .jpg. 

http : //www . chem . qmw . ac . uk/surf aces/scc/scat7_6 . htm. 

http : //www. trnmag . com/St or ies/200^./09080^./Nano_memory_scheme_handles_defects_Brief_ 
090804.html. 

http : //www. chem . northwest em . edu/~mkngrp/dpn . htm. 

http: //sere, carleton. edu/usingdata/nasaimages/index^.html. 
Diagram of an STM [4]. 

http : //www. foresight . org/Conferences/MNT7/Abstracts/Levi/. 
http : //www . weizmann . ac . il/chemphys/kral/nano2 .jpg. 

http : //www. physics . umd. edu/lecdem/outreach/QOTW/pics/k3-06 . gif. 



www.ckl2.org 164 



Chapter 2 

Clear Sunscreen- Teacher 
Materials 



2.1 How Light Interacts with Matter 

Unit Overview 

Contents 

For Anyone Planning to Teach Nanoscience...Read This First! 

Clear Sunscreen Overview, Learning Goals & Standards 

Unit at a Glance: Suggested Sequencing of Activities for Full Unit 

Alignment of Unit Activities with Learning Goals 

Alignment of Unit Activities with Curriculum Topics 

List of Sunscreen Products that use Nanoparticle Ingredients 

(Optional) Clear Sunscreen Pretest/Posttest: Teacher Answer Sheet 

For Anyone Planning to Teach Nanoscience... Read This First! 

Nanoscience Denned 

Nanoscience is the name given to the wide range of interdisciplinary science that is exploring the special 
phenomena that occur when objects are of a size between 1 and 100 nanometers (10~ 9 m) in at least 
one dimension. This work is on the cutting edge of scientific research and is expanding the limits of our 
collective scientific knowledge. 

Nanoscience is "Science-in-the-Making" 

Introducing students to nanoscience is an exciting opportunity to help them experience science in the mak- 
ing and deepen their understanding of the nature of science. Teaching nanoscience provides opportunities 
for teachers to: 

• Model the process scientists use when confronted with new phenomena 

• Address the use of models and concepts as scientific tools for describing and predicting chemical 
behavior 

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• Involve students in exploring the nature of knowing: how we know what we know, the process of 
generating scientific explanations, and its inherent limitations 

• Engage and value our student knowledge beyond the area of chemistry, creating interdisciplinary 
connections 

One of the keys to helping students experience science in action as an empowering and energizing experience 
and not an exercise in frustration is to take what may seem like challenges of teaching nanoscience and turn 
them into constructive opportunities to model the scientific process. We can also create an active student- 
teacher learning community to model the important process of working collaboratively in an emerging area 
of science. 

This document outlines some of the challenges you may face as a teacher of nanoscience and describes 
strategies for turning these challenges into opportunities to help students learn about and experience 
science in action. The final page is a summary chart for quick reference. 

Challenges & Opportunities 

1. You will not be able to know all the answers to student (and possibly your own) questions 
ahead of time ... 

Nanoscience is new to all of us as science teachers. We can (and definitely should) prepare ahead of time 
using the resources provided in this curriculum as well as any others we can find on our own. However, it 
would be an impossible task to expect any of us to become experts in a new area in such a short period of 
time or to anticipate and prepare for all of the questions that students will ask. 

... This provides an opportunity to model the process scientists use when confronted with 
new phenomena. 

Since there is no way for us to become all-knowing experts in this new area, our role is analogous to the 
"lead explorer" in a team working to understand a very new area of science. This means that it is okay 
(and necessary) to acknowledge that we don't have all the answers. We can then embrace this situation 
to help all of our students get involved in generating and researching their own questions. This is a very 
important part of the scientific process that needs to occur before anyone steps foot in a lab. Each time 
we teach nanoscience, we will know more, feel more comfortable with the process for investigating what 
we don't know, and find that there is always more to learn. 

One strategy that we can use in the classroom is to create a dedicated space for collecting questions. This 
can be a space on the board, on butcher paper on the wall, a question "box" or even an online space if 
we are so inclined. When students have questions, or questions arise during class, we can add them to the 
list. Students can be invited to choose questions to research and share with the group, we can research 
some questions ourselves, and the class can even try to contact a nanoscientist to help us address some of 
the questions. This can help students learn that conducting a literature review to find out what is already 
known is an important part of the scientific process. 

2. Traditional chemistry and physics concepts may not be applicable at the nanoscale level 

One way in which both students and teachers try to deal with phenomena we don't understand is to go 
back to basic principles and use them to try to figure out what is going on. This is a great strategy as long 
as we are using principles and concepts that are appropriate for the given situation. 

However, an exciting but challenging aspect of nanoscience is that matter acts differently when the particles 
are nanosized. This means that many of the macro-level chemistry and physics concepts that we are used 
to using (and upon which our instincts are based) may not apply. For example, students often want to 
apply principles of classical physics to describe the motion of nanosized objects, but at this level, we know 
that quantum mechanical descriptions are needed. In other situations it may not even be clear if the 

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macroscale-level explanations are or are not applicable. For example, scientists are still exploring whether 
the models used to describe friction at the macroscale are useful in predicting behavior at the nanoscale 
(Luan & Robbins, 2005). 

Because students don't have an extensive set of conceptual frameworks to draw from to explain nanophe- 
nomena, there is a tendency to rely on the set of concepts and models that they do have. Therefore, there 
is a potential for students to incorrectly apply macroscale-level understandings at the nanoscale level and 
thus inadvertently develop misconceptions. 

... This provides an opportunity to explicitly address the use of models and concepts as 
scientific tools for describing and predicting chemical behavior. 

Very often, concepts and models use a set of assumptions to simplify their descriptions. Before applying 
any macroscale-level concept at the nanoscale level, we should have the students identify the assumptions 
it is based on and the situations that it aims to describe. For example, when students learn that quantum 
dots fluoresce different colors based on their size, they often want to explain this using their knowledge 
of atomic emission. However, the standard model of atomic emission is based on the assumption that the 
atoms are in a gaseous form and thus so far apart that we can think about their energy levels independently. 
Since quantum dots are very small crystalline solids, we have to use different models that think about the 
energy levels of the atoms together as a group. 

By helping students to examine the assumptions a model makes and the conditions under which it can be 
applied, we not only help students avoid incorrect application of concepts, but also guide them to become 
aware of the advantages and limitations of conceptual models in science. In addition, as we encounter 
new concepts at the nanoscale level, we can model the way in which scientists are constantly confronted 
with new data and need to adjust (or discard) their previous understanding to accommodate the new 
information. Scientists are lifelong learners and guiding students as they experience this process can help 
them see that it is an integral and necessary part of doing science. 

3. Some questions may go beyond the boundary of our current understanding as a scientific 
community... 

Traditional chemistry curricula primarily deal with phenomena that we have studied for many years and 
are relatively well understood by the scientific community. Even when a student has a particularly deep or 
difficult question, if we dig enough we can usually find ways to explain an answer using existing concepts. 
This is not so with nanoscience! Many questions involving nanoscience do not yet have commonly agreed 
upon answers because scientists are still in the process of developing conceptual systems and theories to 
explain these phenomena. For example, we have not yet reached a consensus on the level of health risk 
associated with applying powders of nanoparticles to human skin or using nanotubes as carriers to deliver 
drugs to different parts of the human body. 

... This provides an opportunity to involve students in exploring the nature of knowing: how 
we know what we know, the process of generating scientific explanations, and its inherent 
limitations. 

While this may make students uncomfortable, not knowing a scientific answer to why something happens 
or how something works is a great opportunity to help them see science as a living and evolving field. 
Highlighting the uncertainties of scientific information can also be a great opportunity to engage students 
in a discussion of how scientific knowledge is generated. The ensuing discussion can be a chance to talk 
about science in action and the limitations on scientific research. Some examples that we can use to begin 
this discussion are: Why do we not fully understand this phenomenon? What (if any) tools limit our ability 
to investigate it? Is the phenomenon currently under study? Why or why not? Do different scientists have 
different explanations for the same phenomena? If so, how do they compare? 

4. Nanoscience is a multidisciplinary field and draws on areas outside of chemistry, such as 

167 www.ckl2.org 



biology, physics, and computer science... 

Because of its multidisciplinary nature, nanoscience can require us to draw on knowledge in potentially 
unfamiliar academic fields. One day we may be dealing with nanomembranes and drug delivery systems, 
and the next day we may be talking about nanocomputing and semiconductors. At least some of the many 
areas that intersect with nanoscience are bound to be outside our areas of training and expertise. 

... This provides an opportunity to engage and value our student knowledge beyond the 
traditional areas of chemistry. 

While we may not have taken a biology or physics class in many years, chances are that at least some of 
our students have. We can acknowledge students' interest and expertise in these areas and take advantage 
of their knowledge. For example, ask a student with a strong interest in biology to connect drug delivery 
mechanisms to their knowledge about cell regulatory processes. In this way, we share the responsibility for 
learning and emphasize the value of collaborative investigation. Furthermore, this helps engage students 
whose primary area of interest isn't chemistry and gives them a chance to contribute to the class discussion. 
It also helps all students begin to integrate their knowledge from the different scientific disciplines and 
presents wonderful opportunities for them to see the how the different disciplines interact to explain real 
world phenomena. 

Final Words 

Nanoscience provides an exciting and challenging opportunity to engage our students in cutting edge science 
and help them see the dynamic and evolving nature of scientific knowledge. By embracing these challenges 
and using them to engage students in meaningful discussions about science in the making and how we 
know what we know, we are helping our students not only in their study of nanoscience, but in developing 
a more sophisticated understanding of the scientific process. 

References 

• Luan, B., & Robbins, M. (2005, June). The breakdown of continuum models for mechanical contacts. 
Nature 435, 929-932. 

Table 2.1: Challenges of teaching nanoscience and strategies for turning these challenges into 
learning opportunities. 

THE CHALLENGE... PROVIDES THE OPPORTUNITY TO... 

1. You will not be able to know all the answers to Model the process scientists use when confronted 

student (and possibly your own) questions ahead with new phenomena: 

of time Identify and isolate questions to answer 

Work collectively to search for information using 
available resources (textbooks, scientific journals, 
online resources, scientist interviews) 
Incorporate new information and revise previous 
understanding as necessary 
Generate further questions for investigation 



www.ckl2.org 168 



Table 2.1: (continued) 



THE CHALLENGE... 



PROVIDES THE OPPORTUNITY TO... 



2. Traditional chemistry and physics concepts may 
not be applicable at the nanoscale level 



3. Some questions may go beyond the boundary of 
our current understanding as a scientific commu- 
nity 



4. Nanoscience is a multidisciplinary field and 
draws on areas outside of chemistry, such as bi- 
ology and physics 



Address the use of models and concepts as scien- 
tific tools for describing and predicting chemical 
behavior: 

Identify simplifying assumptions of the model and 
situations for intended use 

Discuss the advantages and limitations of using 
conceptual models in science 

Integrate new concepts with previous understand- 
ings 

Involve students in exploring the nature of know- 
ing: 

How we know what we know 

The limitations and uncertainties of scientific ex- 
planation 

How science generates new information 
How we use new information to change our under- 
standings 

Engage and value our student knowledge beyond 
the area of chemistry: 

Help students create new connections to their ex- 
isting knowledge from other disciplines 
Highlight the relationship of different kinds of in- 
dividual contributions to our collective knowledge 
about science 

Explore how different disciplines interact to explain 
real world phenomena 



Clear Sunscreen: Overview, Learning Goals &; Standards 

Type of Courses: Chemistry, Physics 

Grade Levels: 9-12 

Topic Area: The interaction of light and matter 

Key Words: Nanoscience, nanotechnology, light scattering, electromagnetic spectrum, organic com- 
pounds, inorganic compounds 

Time Frame: 6 class periods (assuming 50 - minutes classes), with extensions available 

Overview 

Traditional inorganic sunscreens use "large" zinc oxide particles which effectively block the full spectrum of 
ultraviolet (UV) light, but also scatter visible light, giving the cream an undesirable white color. Because 
of this, people often apply too little sunscreen or choose another, less effective, kind. If nanosized particles 
of zinc oxide are used instead, the cream is transparent because the diameter of each nanoparticle is much 



169 



www.ckl2.org 



smaller than the wavelength of visible light and thus does not scatter the light. Given our increased 
awareness of the dangers of long wave ultraviolet (UVA) light (which many other sunscreens do not block), 
a full spectrum sunscreen that people are willing to use is an important tool for preventing skin cancer. 

Enduring Understandings (EU) 

What enduring understandings are desired? Students will understand: 

1. How the energies of different wavelengths of light interact differently with different kinds of matter. 

2. Why particle size can affect the optical properties of a material. 

3. That there may be health issues for nanosized particles that are undetermined at this time. 

4. That it is possible to engineer useful materials with an incomplete understanding of their properties. 

5. There are often multiple valid theoretical explanations for experimental data; to find out which one 
works best, additional experiments are required. 

6. How to apply their scientific knowledge to be an informed consumer of chemical products. 

Essential Questions (EQ) 

What essential questions will guide this unit and focus teaching and learning? 

1. What are the most important factors to consider in choosing a sunscreen? 

2. How do you know if a sunscreen has "nano" ingredients? 

3. How do "nano" sunscreen ingredients differ from most other ingredients currently used in sunscreens? 

Key Knowledge and Skills (KKS) 

What key knowledge and skills will students acquire as a result of this unit? Students will be able to: 

1. Describe the mechanisms of absorption and scattering by which light interacts with matter. 

2. Describe how particle size, concentration and thickness of application affect how particles in a sus- 
pension scatter light. 

3. Explain how the phenomenon of seeing things in the world is a human visual response depending on 
how light interacts with objects. 

4. Evaluate the relative advantages (strong blockers, UVA protection) and disadvantages (possible car- 
cinogenic effects, not fully researched) of using nanoparticulate sunscreens. 

Prerequisite Knowledge 

This unit assumes that students are familiar with the following concepts or topics: 

1. Atoms, molecules, ionic and covalent compounds 

2. Atomic energy levels, absorption of light 

3. Light waves, frequencies, electromagnetic spectrum, color 

NSES Content Standards Addressed 

K-12 Unifying Concepts and Process Standard 

As a result of activities in grades, K-12, all students should develop understanding and abilities aligned 
with the following concepts and processes: (2 of the 5 categories apply) 

• Evidence, models and explanation 

• Form and function 

www.ckl2.org I/O 



Grades 9-12 Content Standard A: Science as Inquiry 

Abilities Necessary to Do Scientific Inquiry 

• Formulate scientific explanations and models. Student inquiries should culminate in formu- 
lating an explanation or model. Models should be physical, conceptual, and mathematical. In the 
process of answering the questions, the students should engage in discussions and arguments that 
result in the revision of their explanations. These discussions should be based on scientific knowledge, 
the use of logic, and evidence from their investigation. (12ASI1.4.) 

• Analyze alternative explanations. This aspect of the standard emphasizes the critical abilities 
of analyzing an argument by reviewing current scientific understanding, weighing the evidence, and 
examining the logic so as to decide which explanations and models are best. In other words, although 
there may be several plausible explanations, they do not all have equal weight. Students should be 
able to use scientific criteria to find the preferred explanations. (12ASI1.5.) 

Understandings about Scientific Inquiry 

• Scientific explanations. Scientific explanations must adhere to criteria such as: a proposed ex- 
planation must be logically consistent; it must abide by the rules of evidence; it must be open to 
questions and possible modification; and it must be based on historical and current scientific knowl- 
edge. (12ASI2.5) 

Grades 9-12 Content Standard B: Physical Science 

Chemical Reactions 

• Energy and chemical reactions. Chemical reactions may release or consume energy. Some 
reactions such as the burning of fossil fuels release large amounts of energy by losing heat and by 
emitting light. Light can initiate many chemical reactions such as photosynthesis and the evolution 
of urban smog. (12BPS3.2) 

Interactions of Energy and Matter 

• Waves. Waves, including sound and seismic waves, waves on water, and light waves, have energy 
and can transfer energy when they interact with matter. (12BPS6.1) 

• Electromagnetic waves. Electromagnetic waves result when a charged object is accelerated or 
decelerated. Electromagnetic waves include radio waves (the longest wavelength), microwaves, in- 
frared radiation (radiant heat), visible light, ultraviolet radiation, x-rays, and gamma rays. The 
energy of electromagnetic waves is carried in packets whose magnitude is inversely proportional to 
the wavelength. (12BPS6.2) 

• Discrete amounts of energy in atoms/molecules. Each kind of atom or molecule can gain or 
lose energy only in particular discrete amounts and thus can absorb and emit light only at wave- 
lengths corresponding to these amounts. These wavelengths can be used to identify the substance. 
(12BPS6.3) 

Grades 9-12 Content Standard E: Science and Technology 

Understandings about Science and Technology 

• Scientists in different disciplines use different methods. Scientists in different disciplines ask 
different questions, use different methods of investigation, and accept different types of evidence to 

171 www.ckl2.org 



support their explanations. Many scientific investigations require the contributions of individuals 
from different disciplines, including engineering. New disciplines of science, such as geophysics and 
biochemistry often emerge at the interface of two older disciplines. (12EST2.1) 

Grades 9-12 Content Standard F: Science in Personal and Social Perspectives 

Personal and Community Health 

• Personal choice concerning fitness and health involves multiple factors. Personal choice 
concerning fitness and health involves multiple factors. Personal goals, peer and social pressures, 
ethnic and religious beliefs, and understanding of biological consequences can all influence decisions 
about health practices. (12FSPSP1.3) 

Science and Technology in Local, National, and Global Challenges 

• Individuals and society must decide on proposals of new research/technologies. Indi- 
viduals and society must decide on proposals involving new research and the introduction of new 
technologies into society. Decisions involve assessment of alternatives, risks, costs, and benefits and 
consideration of who benefits and who suffers, who pays and gains, and what the risks are and who 
bears them. Students should understand the appropriateness and value of basic questions-"What 
can happen? "-"What are the odds?"-and "How do scientists and engineers know what will happen?" 
(12FSPSP6.4) 

Grades 9-12 Content Standard G: History and Nature of Science 

Nature of Scientific Knowledge 

• All scientific knowledge is subject to change as new evidence becomes available. Because 
all scientific ideas depend on experimental and observational confirmation, all scientific knowledge is, 
in principle, subject to change as new evidence becomes available. The core ideas of science such as 
the conservation of energy or the laws of motion have been subjected to a wide variety of confirmations 
and are therefore unlikely to change in the areas in which they have been tested. In areas where data 
or understanding are incomplete, such as the details of human evolution or questions surrounding 
global warming, new data may well lead to changes in current ideas or resolve current conflicts. In 
situations where information is still fragmentary, it is normal for scientific ideas to be incomplete, 
but this is also where the opportunity for making advances may be greatest. (12GHNS2.3) 

Historical Perspectives 

• Scientific knowledge evolves over time, building on earlier knowledge. The historical 
perspective of scientific explanations demonstrates how scientific knowledge changes by evolving over 
time, almost always building on earlier knowledge. (12GHNS3.4) 

Unit at a Glance: Suggested Sequencing of Activities 

Overview 

The Clear Sunscreen Unit has been designed in a modular fashion to allow you maximum flexibility in 
adapting it to your student's needs. Lessons 1 and 2 provide basic coverage of the dangers of UV exposure, 
the mechanisms by which sunscreens work and the factors that determine their appearance. Combined 

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with Lesson 5 (culminating activities), they make up the basic sequence for the unit. Lessons 3 and 4 are 
each extensions of one of the topics covered in lesson 2 (absorption and appearance) and can be added 
individually to the unit to increase coverage of that topic. 



173 www.ckl2.org 



Table 2.2: 



Lesson 



Basic Sequence 



Optional Extensions 



Lesson 1: Introduction to Sun V 

Protection 

Lesson 2: All About Sunscreens V 

Lesson 3: How Sunscreens Block: 

The Absorption of UV Light 

Lesson 4: How Sunscreens Ap- 
pear: 
Interactions with Visible Light 



V 
V 



Lesson 5: Culminating Activities V 



In addition, most lessons contain an interactive presentation and one or more options for activities so you 
can tailor the depth and duration of the lesson to meet your needs. The following pages contain a suggested 
sequencing of activities for both the basic and full unit, but of course there are many other combinations 
possible. 





Table 2.3: Suggested Sequencing of Activities 


for Basic Unit 




Lesson 


Teaching Days 


Main Ac- 
tivities and 
Materials 


Learning Goals 


Assessment 


Homework 


Lesson 1: In- 


2 days: Day 1 


Sun Protec- 


EU: 1, 6 


Initial Ideas 


Read UV 


troduction to 




tion: Un- 


KKS: 4 


Worksheet 


Protection 


Sun Protection 




derstanding 
the Danger 
PowerPoint 
and Discus- 
sion Initial 
Ideas: Student 
Worksheet 






Lab Activity 
and generate 
hypotheses 




Day 2 


UV Protection 




UV Protection 


Finish UV Pro- 






Lab Activity 




Activity Work- 
sheet 


tection Activ- 
ity Worksheet 


Lesson 2: 


2 days : Day 1 


All About Sun- 


EU: 2, 3, 4, 5, 




Read Sun- 


All About 




screen Power- 


6 




screen Ingredi- 


Sunscreens 




Point and Dis- 
cussion 


KKS: 1, 2, 3, 4 




ents Activity 




Day 2 


Sunscreen 
Ingredients 
Activity Re- 
flection on 
Guiding Ques- 
tions 




Sunscreen 

Ingredients 

Activity 

Worksheet 

Reflection 

on Guiding 

Questions 





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174 



Table 2.3: (continued) 



Lesson 



Teaching Days Main Ac- Learning Goals Assessment 

tivities and 
Materials 



Homework 



Lesson 5: 2 days: Day 1 

Culminating 

Activities 



Consumer EU: 1, 2, 3, 4, Final Reflec- Prepare to 

Choice Project 6 tions Work- share pam- 

(Performance KKS: 1, 2, 3, 4 sheet phlets 

Assessment) Quiz 

OR 

Quiz and Fi- 
nal Reflection 
on Guiding 
Questions 



Day 2 (15 min 
only for quiz 
choice) 



Sharing of 

Consumer 
Choice Pam- 
phlets and Fi- 
nal Reflection 
on Guiding 
Questions 
OR 

Return and re- 
view of quizzes 



Project Scor- 
ing Rubric and 
Peer Feedback 
Form 



Table 2.4: Suggested Sequencing of Activities for Full Unit 



Lesson 


Teaching Days 


Main Ac- 
tivities and 
Materials 


Learning Goals 


Assessment 


Homework 


Lesson 1: In- 


2 days: Day 1 


Sun Protec- 


EU: 1, 


Initial Ideas 


Read UV 


troduction to 




tion: Under- 


6 KKS: 4 


Worksheet 


Protection 


Sun Protection 




standing the 
Danger Pow- 
erPoint and 
Discussion 
Initial Ideas: 
Student Work- 
sheet 






Lab Activity 
and generate 
hypotheses 




Day 2 


UV Protection 




UV Protection 


Finish UV Pro- 






Lab Activity 




Activity Work- 
sheet 


tection Activ- 
ity Worksheet 


Lesson 2: 


2 days : Day 1 


All About Sun- 


EU: 2, 3, 4, 5, 




Read Sun- 


All About 




screen Power- 


6 




screen Ingredi- 


Sunscreens 




Point and Dis- 
cussion 


KKS: 1, 2, 3, 4 




ents Activity 






175 




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Table 2.4: (continued) 



Lesson 


Teaching 


Days 


Main Ac- 
tivities and 
Materials 


Learning Goals 


Assessment 


Homework 




Day 2 




Sunscreen 

Ingredients 

Activity 

Reflection 

on Guiding 

Questions 




Sunscreen 
Ingredients 
Activity Work- 
sheet 
Reflection 
on Guiding 
Questions 


Absorption of 
Light by Mat- 
ter: Student 
Reading 


Lesson 3: How 


1 Day 




Discussion of 


EU: 1 


Reflection 


Scattering 


Sunscreens 






Absorption 


KKS: 1 


on Guiding 


of Light by 


Block: The 






Reading 




Questions 


Suspended 


Absorption of 






How Sun- 






Clusters: Stu- 


UV Light 






screens Block: 
The Absorp- 
tion of UV 
Light Pow- 
erPoint and 
Discussion 
Reflection 
on Guiding 
Questions: 






dent Reading 


Lesson 4: How 


2-3 days: 


Day 


How Sun- 


EU: 1, 2, 6 




Continue 


Sunscreens Ap- 


1 




screens Ap- 


KKS: 1, 2, 3 




to work on 


pear: Interac- 






pear: Inter- 






animations 


tions with Vis- 






actions with 








ible Light 






Visible Light 
PowerPoint 
Slides and 
Discussion 
Introduction 
of Sunscreens 
Animation Ac- 
tivity (creation 
or viewing 
pre-made 
ones) 









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176 



Table 2.4: (continued) 



Lesson 



Teaching Days Main Ac- Learning Goals Assessment 

tivities and 
Materials 



Homework 





Day 2 


Work on 




Animation 


Prepare 


to 






Animation 




worksheet 


present < 


inima- 






Creation 




Reflection 


tions 








OR 




on Guiding 










Discussion 




Questions 










of Pre-Made 














Animations 














and Reflection 














on Guiding 














Questions 










Lesson 4 (con- 


Day 3 [anima- 


Class Presen- 




Animation 






tinued) 


tion creation 
only) 


tation and 

Discussion 

of Student 

Animations 

Reflection 

on Guiding 

Questions 

Reflection 

of Guiding 

Questions 




Scoring Rubric 

Reflection 

on Guiding 

Questions 






Lesson 5: 


2 days: Day 1 


Consumer 


EU: 1, 2, 3, 4, 


Final Reflec- 


Prepare 


to 


Culminating 




Choice Project 


6 KKS: 1, 2, 3, 


tions Work- 


share 


pam- 


Activities 


Day 2 (15 min 
only for quiz 
choice) 


(Performance 
Assessment) 
OR 

Quiz and Fi- 
nal Reflection 
on Guiding 
Questions 

Sharing of 
Consumer 
Choice Pam- 
phlets and Fi- 
nal Reflection 
on Guiding 
Questions 
OR 

Return and re- 
view of quizzes 


4 


sheet 
Quiz 

Project Scor- 
ing Rubric and 
Peer Feedback 
Form 


phlets 





177 



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Table 2.5: 



What enduring understand- 
ings (EU) are desired? Stu- 
dents will understand: 



What essential questions What key knowledge and 

(EQ) will guide this unit and skills (KKS) will students ac- 
focus teaching and learning? quire as a result of this unit? Stu- 

dents will be able to: 



1. How the energies of differ- 
ent wavelengths of light in- 
teract differently with our 
skin and vision. 

2. Why particle size can affect 
the optical properties of a 
material. 

3. That there may be health 
issues for nanosized parti- 
cles that are undetermined 
at this time. 

4. That it is possible to engi- 
neer useful materials with 
an incomplete understand- 
ing of their properties. 

5. There are often multi- 
ple valid theoretical ex- 
planations for experimen- 
tal data; to find out which 
one works best, additional 
experiments are required. 

6. How to apply their scien- 
tific knowledge to be an in- 
formed consumer of chemi- 
cal products. 



1. How do "nano-sunscreens" 
differ from traditional sun- 
screens? 

2. What is the best kind of 
sunscreen to use and why? 

3. Should nanoproducts have 
special regulations associ- 
ated with them? 



1. Describe the mechanism of 
absorption and scattering 
by which light interacts 
with matter. 

2. Describe how particle size, 
concentration and chemical 
/ solvent identity (refrac- 
tive index), affect how par- 
ticles in a suspension scat- 
ter light. 

3. Explain how the phe- 
nomenon of seeing things 
in the world is a human 
visual response depending 
on how light interacts with 
these objects. 

4. Evaluate the relative ad- 
vantages (strong blockers, 
UVA protection) and 
disadvantages (possible 
carcinogenic effects, not 
fully researched) of using 
nanoparticulate sunscreens 



Alignment of Unit Activities with Learning Goals 



Table 2.6: 



Lesson 1 



Lesson 2 



Lesson 3 



Lesson 4 



Lesson 5 



Presentation UV Dangers 

Activity UV Protec- 

tion Lab Ac- 
tivity 



All About 
Sunscreens 
Sunscreen 
Label Activ- 
ity 



Absorption Appearance 

Student Animation Consumer 

Reading Activity Choice 

Project 



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178 



Table 2.6: (continued) 



Lesson 1 



Lesson 2 



Lesson 3 



Lesson 4 



Lesson 5 



Learning 
Goals 



Students will 
understand... 
EU 1. How 
the energies 
of different 
wavelengths 
of light 

interact 
differently 
with differ- 
ent kinds of 
matter. 
EU 2. Why 
particle size 
can affect 
the optical 
properties of 
a material. 
EU 3. That 
there may 
be health 
issues for 
nanosized 
particles 
that are un- 
determined 
at this time. 
EU 4. That 
it is possible 
to engineer 
useful mate- 
rials with an 
incomplete 
understand- 
ing of their 
properties. 



Assessment 



Lab Results/ Label Re- 


Reflection 


Animation/ 


Consumer 


Initial Ideas suits/ Re- 


Worksheet 


Reflection 


Pamphlets/ 


Worksheet flection 




Worksheet 


Quiz 


Worksheet 









179 



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Table 2.6: (continued) 



Lesson 1 



Lesson 2 



Lesson 3 



Lesson 4 



Lesson 5 



EU 5. There 
are often 
multiple 
valid the- 
oretical 
explanations 
for experi- 
mental data; 
to find out 
which one 
work best, 
additional 
experiments 
are required. 
EU6. How 
to ap- 

ply their 
scientific 
knowledge 
to be an 
informed 
consumer 
of chemical 
products. 



Table 2.7: 



Lesson 1 



Lesson 2 



Lesson 3 



Lesson 4 



Lesson 5 





Presentatior 


i UV Dangers 


All About 
Sunscreens 


Absorption 


Appearance 






Activity 


UV Protec- 


Sunscreen 


Student 


Animation 


Consumer 






tion Lab Ac- 


Label Activ- 


Reading 


Activity 


Choice 






tivity 


ity 






Project 


Learning 


Assessment 


Lab Results/ 


Label Re- 


Reflection 


Animation/ 


Consumer 


Goals 




Initial Ideas 


sults/ Re- 


Worksheet 


Reflection 


Pamphlets/ 






Worksheet 


flection 
Worksheet 




Worksheet 


Quiz 


Students will 














able to... 















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180 



Table 2.7: (continued) 



Lesson 1 



Lesson 2 



Lesson 3 



Lesson 4 



Lesson 5 



KKS1. De- 
scribe the 
mechanism 
of absorp- 
tion and 
scattering 
by which 
light inter- 
acts with 
matter 
KKS2. De- 
scribe how 
particle size, 
concentra- 
tion and 
thickness of 
application 
affect how 
particles in 
a suspension 
scatter light. 
KKS3. Ex- 
plain how 
the phe- 
nomenon 
of seeing 
things in 
the world 
is a hu- 
man visual 
response de- 
pending on 
how light in- 
teracts with 
objects. 



181 



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Table 2.7: (continued) 



Lesson 1 



Lesson 2 



Lesson 3 



Lesson 4 



Lesson 5 



KKS4. 

Evaluate 
the relative 
advantages 
(strong 
blockers, 
UVA pro- 
tection) 
and disad- 
vantages 
(possible 
carcinogenic 
effects, not 
fully re- 

searched) 
of using 

nanopar- 
ticulate 
sunscreens 



Alignment of Unit Activities with Curriculum Topics 



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182 



183 www.ckl2.org 



Table 2.8: (continued) 



Unit Topic 


Chapter Topic 


Subtopic Clear Sunscreen Specific Materials 
Lessons 


Table 2.8: Chemistry 


Unit Topic 


Chapter Topic 


Subtopic Clear Sunscreen Specific Materials 
Lessons 



Structure of Mat- Electron Configu- Radiant Energy 
ter ration 



Slides 



www.ckl2.org 



184 



Lesson 1 


. LI: 1-14 (15- 


(LI): In- 


17 optional) 


troduction 


. L2: 2, 16-25 


to Sun 


. L4: All 


Protection 


Slides 


Lesson 2 




(L2): All 


Activity /Handout 


about Sun- 


. LI 


screens 




Lesson 4 


- UV 


(L4): How 


Pro- 




tection 


sunscreens 






Lab 


appear: 




scattering 


Activ- 


Lesson 5 


ity 


(L5): cul- 




minating 


Summary 


activities 


of Sun 




Radia- 




tion 




. L2 




— Light 




Scat- 




tering 




by 3 




Sun- 




screens 




hand- 




out 




Sunscreen 




Ingre- 




dient 




Activ- 




ity 




- FDA 




Ap- 




proved 




Sun- 




screen 




Ingredi- 




ents 



L4 



Table 2.8: (continued) 



Unit Topic 



Chapter Topic 



Subtopic 



Clear Sunscreen Specific Materials 
Lessons 



Structure of Mat- Electron Configu- Quantum Theory 
ter ration 



Lesson 3 

(L3): How 
sunscreens 
block: ab- 
sorption 



Slides 



L2: 8 
L3: 

Slides 
L4: 8, 9 



All 



Chemistry of our Carbon 
World pounds 



Com- Organic 

istry 



Chem- 



Lesson 2 

(L2): All 

About Sun- 
screens 

Lesson 3 

(L3): Ab- 
sorption 



Slides 

. L2: 5-10 
. L3: 5-9 

Activity /Handout 

• L2: Sum- 
mary of FDA 
Approved 
Sunscreen 
Ingredients 



185 



www.ckl2.org 



Table 2.9: Physics 



Mechanics 


Potential Energy 


Absorption Dis- 




Slides 




and Conservation 
of Energy 


persion/scattering 


• Lesson 2 
(L2): All 
About Sun- 
screens 

• Lesson 3 
(L3): The 
Science 
Behind 
Sunscreen 
Protection: 
Absorption 

• Lesson 4 
(L4): The 
Science 
Behind 
Sunscreen 
Appearance: 
Scattering 


. L2: 8-10, 14, 
18-24 

• L3: (most) 

• L4: (most) 

Activity 

• Sunscreen 
Animation 


Atomic Physic 


Atomic Models 


Electromagnetic 




Slides 






spectrum Fre- 
quency/ wave- 
length 


• Lesson 1 
(Ll): In- 
tro to Sun 
Protection 


. Ll: 7 


Electricity and 


Electromagnetic 


Photoelectric 




Slides 


Magnetism 


Waves 


effect E = hf; 
energy levels 


• Lesson 3 


. L3: 3, 6-7, 



(L3): The 

Science 

Behind 

Sunscreen 

Protection: 

Absorption 

Lesson 4 

(L4): The 

Science 

Behind 

Sunscreen 

Appearance: 

Scattering 



14 

L4: 5, 8 



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186 



187 www.ckl2.org 



Table 2.10: (continued) 



Unit Topic 


Chapter Topic Subtopic Clear Sunscreen Specific Materials 

Lessons 


Table 2.10: Environmental Science 


Unit Topic 


Chapter Topic Subtopic Clear Sunscreen Specific Materials 

Lessons 



Atmosphere and 
Climate Energy 



The Ozone Shield 



The Ozone Hole: 
The Effects of 
Ozone Thinning 



Slides 



Lesson 1 


. L1-L4: All 


(LI): In- 


slides 


tro to Sun 






Protection 


Activity /Handout 


Lesson 2 


. LI: 


UV 


(L2): All 


Bead Lab 


About Sun- 


. L2: 




screens 






Lesson 3 






(L3): How 




Sunscreen 


Sunscreens 




ingre- 


Block: Ab- 




dients 


sorption 




Activ- 


Lesson 4 




ity 


(L4): How 




- Light 


Sunscreen 




Scat- 






Appear: 




tering 


Scattering 




by 


Lesson 5 




Three 


(L5): Ad 




Sun- 


Campaign 




screens 


Project 




Reflection 
on the 
Guid- 
ing 
Ques- 
tions 



L3: 



Reading: 
Ab- 
sorp- 
tion of 
Light 

by 
Matter 



www.ckl2.org 



188 



Reflecting 
on the 
Guid- 
ing 
Ques- 
tions 



Table 2.10: (continued) 



Unit Topic Chapter Topic Subtopic Clear Sunscreen Specific Materials 

Lessons 



189 www.ckl2.org 



www.ckl2.org 190 



Table 2.11: (continued) 



Unit Topic 


Chapter Topic 


Subtopic Clear Sunscreen Specific Materials 
Lessons 


Table 2.11: Biology 


Unit Topic 


Chapter Topic 


Subtopic Clear Sunscreen Specific Materials 
Lessons 



The Human Body 



Skeletal, Muscu- 


The Integumen- 




Slides 


lar, and Integu- 
mentary System 


tary System 


• Lesson 1 
(LI): In- 


• 


LI, L2, L4: 
All slides 






tro to Sun 


• 


L3: Use with 






Protection 




instructor 's 






• Lesson 2 




discretion 






(L2): All 




flj 






About Sun- 
screens 


Activity /Handout 






• Lesson 3 
(L3): How 


• 


LI: UV 
Bead Lab 






Sunscreens 
Block: Ab- 


• 


L2: 






sorption 
• Lesson 4 




Sunscreen 






(L4): How 

Sunscreen 

Appear: 




Ingre- 
dients 
Activ- 






Scattering 
• Lesson 5 
(L5): Cul- 
minating 




ity 
— Light 
Scat- 
tering 






Activities 
(Optional) 


• 
• 


by 

Three 
Sun- 
screens 

Reflections 
on the 
Guid- 
ing 
Ques- 
tions 

L3: Use with 
instructor 's 
discretion 

[1] 
L4: 

Reading: 
Scat- 




191 






tering 
www 0? k4g fi rg 

Parti- 
cles 



Table 2.11: (continued) 



Unit Topic Chapter Topic Subtopic Clear Sunscreen Specific Materials 

Lessons 



[1] Clear Sunscreen Lesson 3 requires some schema of chemistry and physics and can be used with biology 
students but this is at the instructor's discretion. Instructor should gauge student's depth of understanding 
behind the chemistry and physics concepts used in this particular lesson. 

(All Sunscreens listed as: Brand - Products) 

Sunscreens that use nanoparticulate ZnO and/or TiOi as their only active ingredients: 

Alba Botanica - Sun (sold at Trader Joes) 

Clinique - Super City Block 

Fallene - Total Block Suncare Line 

Peter Thomas Roth - Ultra-Lite Titanium Dioxide Sunblock 

Blue Lizard - Sensitive Sunscreen 

SkinCeuticals - Daily Sun Defense 

Team Estrogen - All Terrain TerraSport Sunblock 

SunSmart - Therapeutics Line 

Wet Dreams - All Natural Sunscreen Line (Australian Surf Brand) 

Sunscreens that use nanoparticulate ZnO and/or TiOi as one of their active ingredients along with organic 
ingredients: 

Dermatone - All products 

Banana Boat - "Surf" and Sensitive Skin Sunscreens 

Long's - Ski & Surf Sunscreen 

BullFrog - SPF 45 

Banana Boat - BabyMagic and Kids Sunscreen 

Coppertone - Spectra 3 

No Ad - Kids Sunblock 

Panama Jack - Surf N Sport Clear Zinc 

Clear Sunscreen Pretest/Posttest: Teacher Answer Sheet 

20 points total 

1. In what ways are "nano" sunscreen ingredients similar and different from other ingredients currently 
used in sunscreens? For each of the four categories below, indicate whether "nano" sunscreen ingredients 
are "similar" or "different" to organic and inorganic ingredients and explain how. (1.5 points each, total 
of 12 points) 

Table 2.12: 



Organic Ingredients (e.g. PABA) Inorganic Ingredients (e.g. Clas- 
sic Zinc Oxide used by lifeguards) 



Chemical Structure Similar or Different Similar or Different 



www.ckl2.org 192 



Table 2.12: (continued) 



Organic Ingredients (e.g. PABA) 



Inorganic Ingredients (e.g. Clas- 
sic Zinc Oxide used by lifeguards) 



Kinds of Light Blocked 



Way Light is Blocked 



Appearance on the Skin 



How: Nano ingredients are small 
ionic clusters while organic ingre- 
dients are molecules. 

Similar or Different 
How: Organic ingredients each 
block a small part of the UV 
spectrum (generally UVB) while 
nano ingredients block almost 
the whole thing, 
Similar or Different 
How: Both nano and organic in- 
gredients block UV light via ab- 
sorption. (The specific absorp- 
tion mechanism is different, but 
students are not expected to re- 
port this) 

Similar or Different 
How: Both nano and organic 
ingredients appear clear on the 
skin. 



How: Nano ingredients are a 
kind of inorganic ingredients. 
Bother are ionic clusters but the 
nano clusters are smaller. 
Similar or Different 
How: Both nano ingredients and 
traditional inorganic ingredients 
block almost the whole UV spec- 
trum. 

Similar or Different 

How: Both nano and inorganic 

ingredients block UV light via 

absorption. 



Similar or Different 
How: Traditional inorganic in- 
gredients appear white on the 
skin while nano ingredients ap- 
pear clear. 



2. Briefly describe one benefit and one drawback of using a sunscreen that contains "nano" ingredients: (1 
point each, a total of 2 points) 

Benefits: 

• Block whole UV spectrum 

• Appear clear, people less likely to under apply 

Drawbacks: 

• New chemicals not fully studied; possible harmful effects still unknown. FDA is not treating nano- 
versions of known chemicals as new; needed health studies may not occur. 

• Very small particles are more likely to cross membranes and get into unintended parts of the body 

3. What determines if a sunscreen appears white or clear on your skin? (4 points) 
Answer: 

• Particle size. 



Explanation: 



Particles whose diameters are « 1/2 A are most likely to scatter light of that wavelength. 

193 www.ckl2.ors 



• Since visible light has A * 400 - 800 nm, particles with a diameter of 200 - 400 nm (traditional 
inorganic ingredients) scatter visible light the most. The scattered rays that are reflected towards 
our eyes are of all colors in the spectrum, making the sunscreen appear white. 

• Particles smaller than 100 nm in diameter (nano and organic ingredients) do not scatter light appre- 
ciably. The sunlight passes through them and reaches our skin where the blue/green wavelengths are 
absorbed. The red/orange/yellow wavelengths are reflected towards our eyes making the skin appear 
its characteristic color. 

4. How do you know if a sunscreen has "nano" ingredients? (2 points) 

Ingredients list contains inorganic ingredients (zinc oxide or titanium dioxide) and sunscreen appears clear 
on the skin. 

Introduction to Sun Protection 

Contents 

• Introduction to Sun Protection: Teacher Lesson Plan 

• Sun Protection: Understanding the Danger: PowerPoint with Teacher Notes 

• Clear Sunscreen Initial Ideas: Teacher Instructions 

• Ultra- Violet (UV) Protection Lab Activity: Teacher Instructions & Answer Key 

Teacher Lesson Plan 

Orientation 

This lesson is an introduction to the context and need for sunscreen and the important health concerns it 
is designed to address. The goal is to spark students' interest by addressing a topic of personal significance 
and get them to draw on their existing knowledge to generate initial ideas about the driving questions of 
the unit. They will refine this understanding over the course of the unit and have a chance to reflect on 
their initial thoughts at the end of the unit. 

• The Sun Protection: Understanding the Danger PowerPoint slide set explains the danger of skin 
cancer and the need to use sunscreen to protect our bodies. A brief introduction to the different 
kinds of electromagnetic waves and their energies sets the stage for differentiating between the two 
kinds of UV light from which we need to protect our bodies (UVA and UVB). The final slide in the 
set introduces the driving questions for the unit. 

• The Summary of Radiation Emitted by the Sun: Student Handout is a useful tool for students to 
refer to throughout the unit to remind them of the key differences between radiation types. 

• The Initial Ideas Worksheet gives students the chance to draw on their existing knowledge to formulate 
first thoughts about the unit. This is a great tool for eliciting students' prior knowledge (and possible 
misconceptions) related to the unit topics. 

• The Ultra- Violet (UV) Protection Lab Activity gives students the chance to explore UV protection 
first hand by testing the strength of different kinds of blocking substances (for example sunscreens 
and tee-shirts) with UV sensitive beads. 

Essential Questions (EQ) 

What essential questions will guide this unit and focus teaching and learning? 

1. What are the most important factors to consider in choosing a sunscreen? 

www.ckl2.org 194 



2. How do you know if a sunscreen has "nano" ingredients? 

3. How do "nano" sunscreen ingredients differ from most other ingredients currently used in sunscreens? 

Enduring Understandings (EU) 

Students will understand: 

(Numbers correspond to learning goals overview document) 

1. How the energies of different wavelengths of light interact differently with different kinds of matter. 

6. How to apply their scientific knowledge to be an informed consumer of chemical products 

Key Knowledge and Skills (KKS) 

Students will be able to: 

(Numbers correspond to learning goals overview document) 

4. Evaluate the relative advantages (strong blockers, UVA protection) and disadvantages (possible car- 
cinogenic effects, not fully researched) of using nanoparticulate sunscreens. 

Table 2.13: Introduction & Initial Ideas Timeline 



Day 



Activity 



Time 



Materials 



Day 1 (50 min) 



Show the Sun Protec- 30 min 
tion: Understanding 

the Danger PowerPoint 
Slides, using the em- 
bedded question slides 
and teacher's notes to 
start class discussion. 
At the end of the pre- 
sentation, hand out the 
Summary of Radiation 
Emitted by the Sun 
for students to refer to 
throughout the unit. 

Hand out the Clear 10 min 
Sunscreen Initial Ideas: 
Student Worksheet and 
have students work 
alone or in pairs to 
brainstorm answers to 
the driving questions. 
Let students know that 
at this point they are 
just brainstorming ideas 
and they are not ex- 
pected to be able to 
fully answer the ques- 
tions. 



Sun Protection: Un- 
derstanding the Dan- 
ger PowerPoint Slides & 
Teacher Notes 
Computer and projector 
Copies of Summary of 
Radiation Emitted by 
the Sun: Student Hand- 
out 



Copies of Clear Sun- 
screen Initial Ideas: 
Student Worksheet 
Clear Sunscreen Initial 
Ideas: Teacher Instruc- 
tions 



195 



www.ckl2.org 



Table 2.13: (continued) 



Day 



Activity 



Time 



Materials 



Return to whole class 
discussion and have stu- 
dents share their ideas 
with the class to make 
a "master list" of initial 
ideas. The goal is not 
only to have students 
get their ideas out in the 
open, but also to have 
them practice evaluat- 
ing how confident they 
are in their answers. 
This is also a good 
opportunity for you to 
identify any miscon- 
ceptions that students 
may have to address 
throughout the unit. 



10 min 



Day 2 (50 min) 



Student Homework: 15 min 

Read the UV Pro- 
tection Lab Activity: 
Student Instructions & 
Worksheet and fill in 
the Hypothesis section. 
Ask if students have 10 min 
any questions about the 
lab. Have the students 
share their hypotheses 
and the rationales be- 
hind them. 

Have students work 30 min 
through the lab in 
teams of 2 or 3. Af- 
ter students have 
completed the data 
collection, they should 
work on the analysis 
section in their teams. 



Copies of UV Protection 
Lab Activity: Student 
Instructions & Work- 
sheet 



UV Protection Lab Ac- 
tivity: Teacher Instruc- 
tions & Answer Key 



Lab Materials (as listed 
in the UV Protection 
Lab Activity: Teacher 
Instructions & Answer 
Key) 

Note that some materi- 
als may need to be or- 
dered ahead of time 



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196 



Table 2.13: (continued) 



Day 



Activity 



Time 



Materials 



Have students share 
their analysis graphs 
with the whole class. 
Discuss the different 
results of the different 
groups and possible 
explanations for the 
results found. 
If there is time, combine 
the whole class's data 
into one super graph. 



10 min 



Student Homework: 
Complete the Con- 
clusion section of the 
lab 



30 min 



Sun Protection 




Understanding the Danger 

Why use sunscreen? 

Too Much Sun Exposure is Bad for Your Body 

• Premature skin aging (wrinkles) 

• Sunburns 

• Skin cancer 

• Cataracts 

Skin Cancer Rates are Rising Fast 
Skin cancer: 

• ~ 50% of all cancer cases 



197 



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Figure 2.1 



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198 




199 



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Probability of getting skin cancer 



1930 : 


: 1 


in 


5,00 


2004 : 


: 1 


in 


65/ 


205' 


1 


in 


>n... 




Figure 2.3 



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200 



• > 1 million cases each year 

• ~ 1 person dies every hour 

Causes of the increase: 

• Decrease ozone protection 

• Increased time in the sun 

• Increased use of tanning beds 

(Sources: http : //www . msnbc . msn . com/ id/837929 1/s it e/newsweek/ http : //www . skincarephysicians . 
com/skincancernet /what is. html http://www.msu.edu/~aslocum/sun/skincancer.htm) 

What are sun rays? 

How are they doing damage? 

The Electromagnetic Spectrum 

• Sun rays are electromagnetic waves 

— Each kind has a wavelength, frequency and energy 



bcrwwng wgy 



I 



Inc 




0.0001 inn 0.01 mi 



10 nm tOOOnm 0.01 en tern Im KM hi 



todot TV FM AM 




Note: Otagrar- era*n 
cr a b^airprtc scale 

IR 



401 na 



Figure 2.4 



The Sun's Radiation Spectrum I 



• The sun emits several kinds of electromagnetic radiation 

- Infrared (IR), Visible (Vis), and Ultra Violet (UV) 

• Higher energy radiation can damage our skin 
The Sun's Radiation Spectrum II 



201 



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Figure 2.5 



c 






o 






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T3 






(D 






K 






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uv 


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rn 


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^ .«.- 


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c 

3 
O 






E 


lv: ^^fl 




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Wavelength of Light (X) in nm 
Higher Energy 



Figure 2.6 



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202 



• How much UV, Vis & IR does the sun emit? 

Does all the radiation from the sun reach the earth? 
The Earth's Atmosphere Helps Protect Us 




Figure 2.7 



• Some of the sun's radiation is absorbed by particles in earth's atmosphere 

— Water vapor (H2O) absorbs IR rays 

— Ozone (O3) absorbs some UV rays 

— Visible rays just pass through 

• Challenge Questions 

1. What happens if the Ozone layer is partially or completed destroyed? 

2. Why are we concerned about UV, but not IR or visible light? 

How can the sun's rays harm us? 
Sun Rays are Radiation 

• Light radiation is often thought of as a wave with a wavelength (A) and frequency (/) related by this 
equation: 

C = Axf 

• Since c (the speed of light) is constant, the wavelength and frequency are inversely related 

203 www.cki2.0rg 




Figure 2.8 



A=- f=- 

f J * 

• This means that light with a short wavelength will have a high frequency and visa versa 
Radiation Energy I 

EM 
Eocf 




1. Energy Comes in Packets 

• The size of an energy packet (E) is determined by the frequency of the radiation (/) 

E = hxf 

• Radiation with a higher frequency has more energy in each packet 

• The amount of energy in a packet determines how it interacts with our skin 

Radiation Energy II 

2. Total Energy 



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204 



UV INDEX 




Figure 2.9 



205 



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• This relates not only to how much energy is in each packet but also to the total number of packets 
arriving at a given location (such as our skin) 

• Total Energy depends on many factors including the intensity of sunlight 

• The UV Index rates the total intensity of UV light for many locations in the US daily: 

http : //www . epa . gov/sunwise/uvindex . html 
Skin Damage I 




Figure 2.10 

• The kind of skin damage is determined by the size of the energy packet (E = h* f) 

• The UV spectrum is broken into three parts: 

- Very High Energy (UVC) 

- High Energy (UVB) 

- Low Energy (UVA) 

• As far as we know, visible and IR radiation don't harm the skin 
Skin Damage II 

• Very high energy radiation (UVC) is currently absorbed by the ozone layer 

• High energy radiation (UVB) does the most immediate damage (sunburns) 

• Lower energy radiation (UVA) can penetrate deeper into the skin, leading to long term damage 



Sun Radiation Summary I 



UVC 



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Table 2.14: Sun Radiation Summary II 



Radiation 


Characteristic 


Energy 


per 


% of Total Ra- 


Effects on Hu- 


Visible to Hu- 


Type 


Wavelength 


Photon 




diation Emit- 
ted by Sun 


man Skin 


man Eye? 



Increasing Increasing 

Energy Wavelength 

~ 200 - 290 nm High Energy 
(Short-wave 

UV) 



~ 0% (< 1% of DNA Damage No 

all UV) 



206 



Table 2.14: (continued) 



Radiation 


Characteristic 


Energy 


per % of Total Ra- 


Effects on Hu- 


Visible to Hu- 


Type 


Wavelength 


Photon 


diation Emit- 
ted by Sun 


man Skin 


man Eye? 



UVB 


~ 290 - 320 nm 


Medium En- 


~ .35% 


(5% 


of 


Sunburn DNA 




(Mid-range 


ergy 


all UV) 






Damage Skin 




UV) 










Cancer 


UVA 


~ 320 - 400 nm 
(Long-wave 

UV) 


Low Energy 


~ 6.5% ( 
all UV) 


;95% 


of 


Tanning Skin 
Aging DNA 
Damage Skin 
Cancer 


Vis 


~ 400 - 800 nm 


Lower Energy 


-43% 






None Cur- 
rently Known 


IR 


800 - 
120, 000 nm 


Lowest Energy 


-49% 






Heat Sensation 
(high A IR) 



No 



No 



Yes 



No 



With all of this possible damage, it pays to wear sunscreen, but which one should you use? 

There are So Many Choices? 

The Challenge: 3 Essential Questions 

1. What are the most important factors to consider in choosing a sunscreen? 

2. How do you know if a sunscreen has "nano" ingredients? 

3. How do "nano" sunscreen ingredients differ from other ingredients currently used in sunscreens? 



Understanding the Danger: Teacher Notes 

Overview 

This series of interactive slides sets the context for the unit by describing the dangers of UV radiation and 
our need to protect ourselves against them. The final slide presents the three driving questions for the 
lessons in the unit. 

Slide 1: Title Slide 

Questions for Students: Do you wear sunscreen? Why or why not? Are there nanoparticles in your 
sunscreen? How do you know? 

Slide 2: Why Use Sunscreen? (Question Slide) 

Have your students brainstorm ideas about why it is important to use sunscreen. 
Slide 3: Too Much Sun Exposure is Bad for Your Body 

This slide describes the three main dangers of UV radiation: 

• Premature skin aging leads to leathery skin, wrinkles and discolorations or "sun spots." Eyes can also 
be damaged by UV radiation leading to cataracts (damage to the eyes which causes cloudy vision). 

• Sunburns are not only painful but are also a distress response of the skin giving us a signal that 
damage is being done. 

• Skin cancer occurs when UV rays damage DNA in skin cells leading to genetic mutations. The 
mutated cells grow and divide uncontrollably forming a tumor. If caught early, the cancer can be 
removed; otherwise it can spread to other parts of the body and eventually cause death. 



207 



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Penetration of Different Wavelengths 
of Light into Human Skin 



Skin 
layers 

Stratum 



Epl-« n -, 



Cvrnn 



Wavelength of Light 
UVC UVS UV* 



100 MO KB 1W 400 nm 




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o 










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E 


uvc ^^aB 






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1 



Wavelength of Light (a) in nm 

Higner Energy 



Figure 2.12 



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208 




Figure 2.13 






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Broadband Protect ioili^ , agpl 

P ■Saf^ar Children 



SPF 50^™ 
Goes on 








Sunscreen 

T)av 



Figure 2.14 



209 



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Slide 4: Skin Cancer Rates are Rising Fast 

This slide describes the most dangerous consequence of UV radiation - skin cancer. 

It is only recently that being tan came into fashion and that people began to spend time in the sun on 
purpose in order to tan. In addition, clothing today generally reveals more skin than it did in the past. 

The use of tanning beds is not safe and a "base tan" only provides protection of about SPF 4. 

Discussion Question for Students: Are there any other reasons that skin cancer rates might be rising? 

Answer: Improvements in detection technology may mean that we identify more cases inflating the slope 
of the rise. 

Slide 5: What Are Sun Rays? How are they doing damage? (Question Slide) 

Have your students brainstorm ideas about what sun rays are and how they interact with our body. 

Slide 6: The Electromagnetic Spectrum 

Note: The illustrations of the waveforms at the extremes of the wavelength/energy spectrum are not to 
scale. They are simply meant to be a graphical representation of longer and shorter wavelengths. 

You may want to discuss some of the properties and uses of the different parts of the electromagnetic 
spectrum further with your students: 

• Gamma rays result from nuclear reactions and have a very high frequency and energy per photon 
(very short wavelength). Because they have a high energy, the photons can penetrate into cell nuclei 
causing mutations in the DNA. 

• X-rays are produced in collision of high speed electrons and have a high frequency and energy per 
photon (short wavelength). Because they have a smaller energy than gamma rays, the x-ray photons 
can pass through human soft tissue (skin and muscles) but not bones. 

• Ultra Violet Light is produced by the sun and has a somewhat high frequency and energy per photon 
(somewhat short wavelength). Different frequencies of UV light (UVA, UVB) are able to penetrate 
to different depths of human skin. 

• Visible Light is produced by the sun (and light bulbs) and has a medium frequency and energy per 
photon (medium wavelength). Visible light doesn't penetrate our skin, however our eyes have special 
receptors that detect different intensities (brightnesses) and frequencies (colors) of light (how we see). 

• Infrared Light is emitted by hot objects (including our bodies) and have a low frequency and energy 
per photon (long wavelength). Infrared waves give our bodies the sensation of heat (for example 
when you stand near a fire or out in the sun on a hot day.) 

• Radio Waves are generated by running an alternating current through an antenna and have a very 
low frequency and energy per photon (very long wavelength). Because they are of such low energy 
per photon, they can pass through our bodies without interacting with our cells or causing damage. 

Slide 7: The Sun's Radiation Spectrum I 

Sun rays are a form of electromagnetic radiation. Electromagnetic radiation is waves of oscillating electric 
and magnetic fields that move energy through space. 

Discussion Question for Students: What is the difference between UVA, UVB and UVC light? 

Answer: They have different wavelengths, frequencies (UVC: ~ 100-280 nm; UVB: ~ 280-315 nm; UVC 
~ 315 - 400 nm) and thus different energies. 

Note: The division of the UV spectrum (as well as the division of UV, visible, infrared etc.) is a catego- 
rization imposed by scientists to help us think about the different parts of the electromagnetic spectrum, 
which is actually a continuum varying in wavelength and frequency. 

Slide 8: The Sun's Radiation Spectrum II 
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The sun emits primarily UV, visible and IR radiation. < 1% of the sun's radiation is x-rays, gamma waves, 
and radio waves. 

The amount of each kind of light emitted by the sun is determined by the kinds of chemical reactions 
occurring at the sun's surface. 

Slide 9: Does all the radiation from the sun reach the earth? (Question Slide) 

Have your students think about what might happen to the radiation as it travels through space. 

If students bring up the idea of the ozone layer as protecting the earth, ask them to think about how it 
does this. (It does this by absorbing harmful UV rays - in other words capturing their energy so it doesn't 
reach the earth). 

Slide 10: The Earth's Atmosphere Helps Protect Us 

The earth's atmosphere is made up of several layers of gases surrounding the planet. The two closest layers 
are referred to as the troposphere (closest to the earth, where most clouds are found) and the stratosphere 
(farther from the earth, where the protective ozone layer resides). Beyond this there is (in increasing order 
of distance from the earth), the mesosphere, thermosphere and exosphere. 

You may want to remind your students that absorption is the process by which atoms or molecules capture 
radiation energy. 

Answers to Challenge Questions on Slide: 

1. What happens if the Ozone layer is partially or completed destroyed? 

As the ozone layer is depleted, more of the UV light emitted by the sun will reach the earth. UV depletion 
is cause by several chemicals used by humans, particularly the CFCs (chlorofluoro carbons) used in many 
old-style aerosol sprays. Though international agreements limiting the use of such chemicals has helped 
the problem, the fight continues. As the Canadian Space Agency reports, in 2000: 

"Observations showed a strong depletion of the ozone layer over the Arctic, by as much as 60% in some 
layers of the atmosphere. In the lower stratosphere, near the South Pole, the hole reached a record size 
in spring 2000, measuring 28.3 million kilometers. The affected area extended to the southern tip of South 
America. " 

(Source: http : //www . space . gc . ca/asc/eng/sciences/ozone_layer . asp) 

2. Why are we concerned about UV, but not IR or visible light? 

We are concerned about UV radiation because it is higher in energy than IR and visible radiation (this 
will be covered in more detail in the following slides). Even though there is less of it, it has the potential 
to damage humans, while it is currently thought that IR and visible radiation do not. 

Slide 11: How can the sun's rays harm us? (Question Slide) 

Have your students brainstorm ideas about how sun rays might interact with our body. What part(s) of 
our body do they interact with? How do they affect them? 

Slide 12: Sun Rays are Radiation 

If students are not already familiar with the concept of wavelength, it may help to draw a wave on the 
board and indicate that the wavelength is the distance between peaks. 

X 
I 1 




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The speed of light in a vacuum is always the same for all wavelengths and frequencies of light, (c = 
300, 000, 000 m/s) 

You may wish to point out to students that the letter V is the same c in the famous E = mc 2 equation 
showing the relationship between matter and energy. 

You may also want to discuss the concept that all light travels at the same speed in the same medium and 
that this does not depend on the frequency or wavelength of the wave. For example, in other mediums 
(e.g. air, water) light travels slower than in a vacuum. The speed of all light in water is ~ 225,563,909 m/s 
(only 75% of speed in a vacuum.) 

Slide 13: Radiation Energy I 

Example: Imagine that you are outside your friend's window trying to get their attention. You can throw 
small pebbles at the window one after another for an hour and it won't break the window. On the other 
hand, if you throw a big rock just once, you will break the window. It doesn't matter if all the pebbles 
put together would be bigger and heavier than the one rock; because their energy is delivered as separate 
little packets, they don't do as much damage. The same is true with energy packets. 

h is Planck's constant (6.26 x 10~ 34 J s) 

Slide 14: Radiation Energy II 

Total Energy can not be predicted by the frequency of light. 

You may want to talk with your students about the different things that the total energy depends upon. 
For example: time of day (10 am -2 pm is the most direct and strongest sunlight), time of year, amount 
of cloud cover (though some UV always gets through), altitude. 

You may want to explore the UV index site with your students and look at how the index varies by location. 

Slide 15: Skin Damage I 

Discussion Question for Students: Which kinds(s) of UV light do you think we are most concerned 
about and why? 

Answer: The theoretical answer would be UVC > UVB > UVA in terms of concern because of energy 
packet size. This is true for acute (immediate) damage, though as shown in next slide, UVA has now been 
found to cause damage in the long term. UVC is currently not a major concern because it is absorbed by 
the atmosphere and thus doesn't reach our skin. 

Slide 16: Skin Damage II 

Premature aging is caused by damage to the elastic fibers (collagen) in the dermal layer of the skin. Because 
UVA radiation has a lower frequency and thus lower energy per photon, it is not absorbed by the cells of 
the top layer of the skin (the epidermis) and can penetrate deeper into the skin (to the dermis) where it 
does this damage. 

Both UVA and UVB can enter the cell nucleus and cause mutations in the DNA leading to skin cancer. 

Most of the rapid skin regeneration occurs in the epidermal layer. The dermal layer does not regenerate 
as quickly and thus is subject to long term damage. 

Slide 17: Sun Radiation Summary I 

This slide and the following one sum up the differences between the different kinds of radiation emitted by 
the sun. There is a corresponding student handout that students can use as a quick reminder during the 
course of the unit. 

This graph contains the all the information about wavelength, frequency, energy and amount of each kind of 
radiation emitted by the sun. Note that the different "kinds" of radiation are really points on a continuum. 



www.ckl2.org 212 



Common Misconception: We see "black light" (UVA light) because it is close to the visible spectrum. 

The Real Deal: If that were true, we would be able to see all objects as bright under black light and 
that doesn't happen. For example at a party only certain clothes appear bright. What actually happens 
is that black light causes some materials to fluoresce or phosphoresce meaning they absorb the UVA light 
and re-emit violet light in the visible spectrum that our eyes can detect. 

Slide 18: Sun Radiation Summary II 

This slide and the previous one sum up the differences between the different kinds of radiation emitted by 
the sun. There is a corresponding student handout that students can use as a quick reminder during the 
course of the unit. 

This chart summarizes the all the information from the previous graph and lists the effects of each kind of 
radiation on the human body. 

Note: Different diagrams may have different cutoffs for the divisions between UVA, UVB, UVC, visible 
and IR. This is because the electromagnetic spectrum is a continuum and the divisions between categories 
are imposed by scientists, thus not always well agreed upon. 

Example: What determines if it is a "warm" versus a "hot" day? If you set the cutoff at 80 degrees 
Fahrenheit does that mean that a change from 79°F to 81° F is more meaningful than a change from 77°F 
to 79°F? 

Slide 19: With all of this possible damage, it pays to wear sunscreen, but which one should 
you use? (Question Slide) 

Discussion Questions for Students: What do you look for when you are buying a sunscreen and why? 
Do you think that your sunscreen is doing a good job to protect you? 

Answers will vary. The goal of the discussion is for students to get their existing knowledge out on 
the table and to start to think critically about the consumer decisions they make and how they relate to 
science. 

Slide 20: There Are So Many Choices! 

This slide is an animation presenting the many different sunscreens available and the many different claims 
their labels make. 

Slide 21: The Challenge: 3 Essential Questions 

These three questions will guide the upcoming unit: 

1. What are the most important factors to consider in choosing a sunscreen? 

2. How do you know if a sunscreen has "nano" ingredients? 

3. How do "nano" sunscreen ingredients differ from other ingredients currently used in sunscreens? 

Each of the unit activities will help students develop their ideas about the questions. By the end of the 
unit, students should be able to explain and justify their answers to each question. For now, use the Clear 
Sunscreen Initial Ideas Worksheet to gives students the chance to brainstorm their initial answers to these 
questions before they begin the unit. 

Clear Sunscreen Initial Ideas: Teacher Instructions 

The goal of this exercise is to have your students "expose" their current ideas about sunscreens and human 
use of nano-products before they engage in learning activities that will explore these questions. You should 
let your students know that this is not a test of what they know and encourage them to makes guesses 

213 www.ckl2.org 



which they will be able to evaluate based on what they learn in the unit. You may also want to have your 
students share their ideas with the class (there are no "bad" ideas at this stage) and create a giant class 
worksheet of ideas. Students can then discuss whether or not they think each of these statements is true 
and why. 

Write down your initial ideas about each question below and then evaluate how confident you feel that 
each idea is true. At the end of the unit, we'll revisit this sheet and you'll get a chance to see if and how 
your ideas have changed. 

Table 2.15: 

1. What are the How sure are How sure are How sure are End of Unit 

most important you that this is you that this is you that this is Evaluation 

factors to con- true? true? true? 

sider in choos- Not sure Kind-of-Sure Very Sure 
ing a sunscreen? 



2. How do How sure are How sure are How sure are End of Unit 

you know if you that this is you that this is you that this is Evaluation 

true? true? 

Kind-of-Sure Very Sure 



sunscreen true? 

Not sure 



a 

has "nano 

ingredients? 



3. 



How do 



nano sun- 

screen ingre- 

dients differ 

from most other 
ingredients cur- 
rently used in 
sunscreens? 



How sure are How sure are How sure are End of Unit 

you that this is you that this is you that this is Evaluation 

true? true? true? 

Not sure Kind-of-Sure Very Sure 



Ultra- Violet (UV) Protection Lab Activity: Teacher Instructions &: An- 
swer Key 

Summary of Materials to Order Ahead of Time 

Source: Educational Innovations (www.teachersource.com) 

Portable UV light - 1 (#UV-635, $10.95 each) 

Purple UV beads -1 set (#UV-PUR, $6.95 per 250 bead package) 

UV Bead Color Guide - 1 set per lab group (#UV-360, $2.95 each) 

Clear UV blocking glass - 1 set (#FIL-235, $9.95 per set of two discs) 

Introduction 



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214 



It is important to protect our skin from damaging UV radiation, but how do we know how well we are 
protecting ourselves? Is wearing a light shirt at the beach as effective as wearing sunscreen? Is it better 
protection? Do thicker, whiter sunscreens protect us better than transparent sprays? Can we tell how well 
something will block UV by looking at its appearance? 

Lab Explanation 

In this lab students should discover that opacity and UV blocking are not related. Clear substances can 
be UV blockers and some opaque substances are not very good UV blockers. This is true because UV and 
visible light have different wavelengths and frequencies, thus they can interact differently with the same 
substance. 

Research Question 

In this lab you will be investigating the following research question: 

• Does the appearance of a substance (its opacity) relate to its ability to block UV light? 

Opacity 

The opacity of a substance is one way to describe its appearance. Opacity is the opposite of how transparent 
or "see-through" something is; for a completely opaque substance, you cannot see through it at all. Opacity 
is a separate property than the color of a substance - for example, you can have something that is yellow 
and transparent like apple juice or something that is yellow and opaque like cake frosting. 

Hands-On Opacity Examples 

• Yellow frosting and yellow food coloring in water 

• Grape juice (full concentration and several glasses of watered down versions) 

• Stained glass (show different pieces of the same color but varying opacity) 

Hypothesis 

Do you think that UV blocking ability relates to a substance's opacity? Would you expect transparent or 
opaque substances to be better UV blockers? If you are right, what implications does this have for how 
you will protect yourself the next time you go to the beach? Write down your best guesses to answer these 
questions and explain why you think what you think. 

Judging Student Hypotheses 

Student answers may say that they are, are not, or are partially related. Student answers should not be 
judged on the correctness of the hypothesis, but can be evaluated on: 

• The consistency of the answer (if they do relate than they should predict opaque substances to block 
better, if they don't relate, neither group of substances should be expected to be better blockers) 

• Their justification for their answer (are they basing it on personal experience, scientific knowledge, 
etc.) 

Materials 

• Assorted white substances varying in opacity (for example: different sunblocks, sunscreens, sun- 
gels, glass pieces, white t-shirts of varying thicknesses, white tissue paper, white paper of varying 
thicknesses, laundry detergent, white paint, white face makeup) 

• Eight paper cups 

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• One micro spoon 

• Sunscreen Smear Sheet (Xerox form at the end of the lab onto acetate transparencies) 

• Black construction paper (For judging opacity of white substances) 

• UV light source (Available from Educational Innovations, Inc., #UV-635, direct sunlight on a bright 
day will also work) 

• UV sensitive bead testers (Made from the following, instructions below) 

— UV sensitive beads (Available from Educational Innovations, Inc., #UV-PUR) 

— Large wooden craft sticks 

— Super glue 

• UV bead color guide (Available from Educational Innovations, Inc., #UV-360) 

• Cotton swabs (for apply sunscreen to the Sunscreen Smear Sheet) 

• Alcohol wipes (for cleaning sunscreen off the Sunscreen Smear Sheet) 

Making UV Beads into "Bead Testers" 

To make the beads into bead testers you will need to melt them and glue them to wooden craft sticks. 
This makes them much easier for handling and applying sunscreen: 

Here are the directions for melting and mounting the beads as discs. 

1. Preheat oven or toaster oven to 300°F. 

2. Cover a cookie sheet with aluminum foil. 

3. Arrange beads on the cookie sheet. Place them one inch from each other and make sure they are 
laying flat on the sheet. 

4. Place beads in oven and set timer for 15 minutes. 

5. When 15 minutes is over, the beads should have melted and now look like clear discs. 

6. Remove from oven to cool. They will harden to white discs within five minutes. 

7. Using super glue, attach one disc to a large wooden craft stick. Each student group should have three 
disc sticks, one labeled "CI" for Control 1, one labeled "C2" for Control 2, and the third labeled "E" 
for Experimental. 

Alternative Option: Super glue two discs directly onto the UV bead color guide tube. If you choose to 
do this, mount the beads while they are slightly malleable and not cooled completely — approximately 
1-2 minutes after removing melted beads from the oven. 

Choosing Substances for Students to Test 

You will want to have a selection of substances that range in both blocking ability and appearance (from 
clear to opaque). Here are some suggestions of substances to use: 

• "Old" zinc-oxide sunblock that goes on white (As a substitute, Desitin is a cream sold for diaper rash 
that contains 40% zinc oxide.) 

• "New" nano zinc-oxide sunblock that goes on clear 

• A variety of regular sunscreens 

• Clear sunscreen gels or sprays 

• Clear UV blocking glass or plastic (A set of two clear plastic discs, one UV blocking, one not is 
available from Education Innovations, Inc., #FIL-235, $9.95 per set of two discs) 

• White t-shirts of varying thickness 

• Liquid laundry detergent (the ones with whitener will block some UV light) 

• Old white t-shirts (if the old ones have been washed many times with whitening detergent they will 
block some UV light) 

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• White paper of vary thickness (tissue paper, printer paper, construction paper) 

• White paint or white face make-up 

Important Notes on Using Sunscreens 

• Make sure to tell students not to put the sunscreen on their bodies in case of an allergic reaction 

• To avoid mess, you may want to have sunscreens available to students in a bowl or large cup 

Procedure 

Part I: Choose Your Samples 

Goal: Choose a group of substances from the ones provided by your teacher that you think will best help 
you determine if opacity is related to UV blocking. 

• Obtain eight small paper cups. Obtain a small sample of each of the substances you have chosen. 
Label each cup with the name of the substance. 

Tip: Try to choose substances that vary in their opacity and that you would expect to vary in their 
blocking ability. 

Part II: Judge the Opacity 

Goal: To make observations about the appearance (opacity) of the substances you chose, using your eyes 
as the instruments. 

• Obtain a Sunscreen Smear Sheet. Place it on top of a black sheet of paper. 

• Label one square with the name of each substance you are going to test. 

• Use the micro spoon to measure out the first substance (make sure to use an equal amount of all the 
other substances). 

• Then use the cotton swab to smear the substance onto the Sunscreen Smear Sheet, evenly covering 
a whole square with a thin layer. (For solid substances, just place them on top of the sheet). 

• How well can you see through the substance to the black sheet of paper? 

• Use the Opacity Guide on the next page to rank each sample on a 1 to 5 scale. 

Use 5 to represent no opacity (you cannot see the substance at all). 

Use 1 to represent complete opacity (you can't see any black through the sample). 

• Record your observations into the Data Chart in this packet. 

• Repeat for each of your substances. 









5 4 3 


2 


1 



Part III: Test the UV Blocking 

Goal: Use UV-sensitive beads to determine how effective your chosen substances are in blocking UV-light. 

Student Question: Why don't we judge UV blocking ability with our eyes? 

Answer: Because our eyes can't detect UV light, we need to use something that can 



217 



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• Obtain 3 UV bead testers: 

— Bead Tester "CI" for Control 1. This bead will always be kept out of the UV light and will 
show you the lightest color that the bead can be. Keep this in the envelope until you need it. 

— Bead Tester "C2" for Control 2. This bead will always be exposed to the UV light and should 
always change color to let you know that the UV light is reaching the bead. This bead will show 
you the darkest color that the bead can reach. 

— Bead Tester "E" for Experimental. Keep this in its envelope so that it is not exposed to any 
UV light while you are not using it. 

Checking Bead Tester CI and C2 

• Use UV bead color guide to record the initial bead color number (2 - 10) of CI on your data chart. 

• Expose C2 to the UV light for 30 sec. and quickly compare it to the UV bead color guide. Record 
the bead color number (2 - 10) on your data chart. 

Using Bead Tester E with Your Substances 

• To test the UV blocking of a substance, hold Bead Tester E under the square for that substance on 
the Sunscreen Smear Sheet. (For solid substances, just hold Bead Tester E directly behind them). 

• Expose Bead Tester E (covered by the substance) and Bead Tester C2 uncovered) to your UV lamp 
(or direct sunlight) for 30 sees. 

• Take both Bead Testers out of the light, uncover Bead Tester E, and observe any changes to the color 
of the beads using the UV bead color guide. Record the bead color number (2 - 10) for both E and 
C2 on your data chart. 

Tip 

For solid substances, student may confuse the shadow cast by the object with the color change of the bead. 
The best way to accurately judge the color change of a bead with a shadow on it is by placing the color 
guide in the shadow as well. 

• Repeat for each of your substances. 

Data Chart 

Initial CI Bead Color Number 

Initial C2 Bead Color Number 



Table 2.16: 



Substance Appearance Opacity (1 to 5 Color of UV Color of UV Observations 

Name (In- (Describe) rating) bead "E" (2 to bead "C2" (2 and Notes 

elude SPF if 10 rating) to 10 rating) 

applicable) 



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Table 2.16: (continued) 



Substance Appearance Opacity (1 to 5 Color of UV Color of UV Observations 

Name (In- (Describe) rating) bead "E" (2 to bead "C2" (2 and Notes 

elude SPF if 10 rating) to 10 rating) 

applicable) 



Analysis 

Tip 

Students may have difficulties understanding that "no pattern" can be an important and informative 
finding. After giving students a chance to work on the analysis section in their groups, you may want to 
have them come together as a class to discuss their results and focus specifically on what it means to not 
have a pattern and how you know whether you have "no pattern" or "not enough data." If there is time, 
you may want to combine student data into one giant chart and discuss the results with students. 

Now you need to analyze your data to see if it helps to answer the research question: 

Does the appearance of a substance (opacity) relate to its ability to block UV light? One of the ways that 
scientists organize data to help them see patterns is by creating a visual representation. Below you will 
see a chart that you can use to help you analyze your data. 

To fill in the chart, do the following for each substance that you tested: 

1. Find the row that corresponds to its opacity. 

2. Find the column that corresponds to its UV blocking ability. 

3. Draw a large dot • in the box where this row and column intersect. 

4. Label the dot with the name or initials of the substance. 

After you have filled in the chart, answer the analysis questions that follow. 

Table 2.17: 

UV Blocking No Blocking Low Blocking Medium Block- High Blocking Total Blocking 
Ability -> (10) (8) ing (6) (4) (2) 

Opacity J, 
5 Fully Trans- 
parent 
4 
3 
2 
1 Fully Opaque 



1. Look at the visual representation of your data that you have created and describe it. Note any patterns 
that you see. Remember that seeing no pattern can also give you important information. 

Answer 



219 www.ckl2.org 



Ideally the dots will be scattered randomly throughout the graph and not show any pattern. Individual 
data sets may show some concentration of dots in a particular part of the chart due to the substances 
tested, but there should not be a "line" of dots in any direction that would indicate a correlation between 
opacity and UV blocking ability. You may want to discuss with students the difference between a pattern 
(most dots are in the lower left corner) and a relationship (dots form a line showing how one variable varies 
with the other.) 

2. What pattern would you expect to see if there is a relationship between the appearance of a substance 
(opacity) and its ability to block UV light? Draw the pattern by coloring in the grid below. 





Blocking 


>■ 




• 


• 








1 


r 


• 


• 


• 








• 


• 


• 










• 


• 


• 














• 



Tip 

Students might say the opposite (a diagonal line running from the bottom left to the top right indicating 
that more transparent substance block better) which is possible (though counter- intuitive) . If they say 
this, ask them to justify why they think this would be. 

3. Does your chart match the pattern you would expect to see if there is a relationship between opacity 
and UV blocking ability? 

□ Yes 

■ No 

■ I'm not sure 

Tip 

Either the 2 or the 3 answer can be correct; students should not have data that supports a relationship 
between the variables. 

4. What does this answer mean in practical terms? What does it tell you about well you can judge the 
effectiveness of sun protection by looking at its appearance? How might this affect your sun protection 
activities? 

Answer 

The answer of "no pattern" means that you cannot tell how well something will protect you from the sun 
by looking at its appearance. For example, clear sunglasses can provide UV protection to your eyes and 



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220 



a white tee-shirt may not fully protect the skin underneath. This means that it is very important to pay 
attention to SPF (and other) ratings of sun protection and not make assumptions based on appearance. 

5. Do you think that increasing the number of substances you tested would change your answer? Why or 
why not? 

Answer 

No, adding substances will help clarify the answer in situations where the data is not clear, but it should 
not change an answer strongly supported by the data. 

6. How confident are you that the answer you came up with is correct? Do you think that increasing the 
number of substances you tested would change how sure you are of your answer? Why or why not? 

Answer 

Students should discuss their confidence in relation to their data. For example the amount of data points 
they have, the range of substances they tested (and that were available to them). 

More data points would make the existence (or lack of a pattern) more clear. It also increases confidence 
that the data points found were not "flukes" but representative of the overall pool of possible substances 
to test. 

Conclusions 

1. Answer the research question: 
□ Yes, there is a relationship. 

■ No, there is not a relationship. 

■ I'm not sure if there is a relationship. 

Tip 

Either the 2 or the 3 answer can be correct; students should not have data that supports a relationship 
between the variables. 

2. This is how the evidence from the experiment supports my answer: (Make sure to be specific and discuss 
any patterns you do or do not see in the data.) 

Answer 

Students should discuss how their data compares to what data for a pattern would look like. 

3. Identify any extra variables that may have affected your experiment: 

Answer 

Possible answers include the amount (thickness) of sunscreen applied and incomplete cleaning of sunscreen 
from previous trial. 

If you are using natural sunlight, the amount of UV light shining on the beads may also vary between 
trials. If this is the case, students should notice differences in the bead color number for C2 between trials. 

4. How could you control for these variables in future experiments? 
Answer 

Possible answers include measuring sunscreen for application and the use of disposable tester sticks. 

5. What changes would you make to this experiment so that you could answer the research question better? 

Answer 

Possible answers include using more substances (students should give examples) and using better measure- 
ment tools (for example beads with a permanent color change, a digital color reader etc.). 

221 www.ckl2.org 



6. All experiments raise new questions. Sometime these come directly from the experiment and others are 
related ideas that you become curious about. What is a new research question that you would want to 
investigate after completing this experiment? 

Answer 

Possible answers include the relationship between color (hue) and blocking ability, the relationship be- 
tween blocking claims (advertising) and blocking ability and the relationship between amount applied (of 
sunscreen) and blocking ability. 

Table 2.18: Sunscreen Smear Sheet 
Sample: Sample: Sample: Sample: 



Table 2.19: 
Sample: Sample: Sample: Sample: 



Table 2.20: Sunscreen Smear Sheet 

Sample: Sample: Sample: Sample: 



Table 2.21: 
Sample: Sample: Sample: Sample: 

All About Sunscreens 
Teacher Lesson Plan 

Contents 

• All About Sunscreens: Teacher Lesson Plan 

• Sunscreen Ingredients Activity: Teacher Instructions & Answer Key 

• All About Sunscreens: PowerPoint Slides and Teacher Notes 

• Light Reflection by Three Sunscreens: Teacher Answer Key 

• Reflecting on the Guiding Questions: Teacher Instructions & Answer Key 

Orientation 

This lesson introduces students to the difference between organic and inorganic sunscreen ingredients and 
the difference between traditional inorganic ingredients and their nanoversions. These differences include 



www.ckl2.org 222 



their chemical and bonding structure as well as their effectiveness in blocking UV light from reaching the 
skin and their appearance. 

• The All About Sunscreens PowerPoint takes students through the history of why sunscreens were 
first developed, their current rating system for UVB blocking ability (SPF) and the need to also 
consider UVA blocking ability. The slides then explore the different structure and blocking mecha- 
nisms of organic and inorganic sunscreen ingredients. Finally the slides discuss what gives inorganic 
sunscreens their "white" or clear appearance and how the nano versions remedy this situation. There 
is an optional demonstration of absorption of UV light by chemicals in printed money (as an anti- 
counterfeiting measure) embedded in the PowerPoint presentation that you can do with your class. 

• The Sunscreen Ingredients Activity gives students the opportunity to become familiar with the dif- 
ferent ingredients used in sunscreens firsthand. This experience along with the Summary of FDA 
Approved Sunscreen Ingredients Handout is aimed at making students think to look at the ingredients 
on the label the next time they go shopping for a sunscreen. 

• The Reflecting on the Guiding Questions Worksheet asks students to connect their learning from the 
activities in the lesson to the overall driving questions of the unit. 

Essential Questions (EQ) 

What essential questions will guide this unit and focus teaching and learning? 

1. What are the most important factors to consider in choosing a sunscreen? 

2. How do you know if a sunscreen has "nano" ingredients? 

3. How do "nano" sunscreen ingredients differ from most other ingredients currently used in sunscreens? 

Enduring Understandings (EU) 

Students will understand: 

(Numbers correspond to learning goals overview document) 

2. Why particle size can affect the optical properties of a material. 

3. That there may be health issues for nanosized particles that are undetermined at this time. 

4. That it is possible to engineer useful materials with an incomplete understanding of their properties. 

5. There are often multiple valid theoretical explanations for experimental data; to find out which one 
works best, additional experiments are required. 

6. How to apply their scientific knowledge to be an informed consumer of chemical products. 
Key Knowledge and Skills (KKS) 

Students will be able to: 

(Numbers correspond to learning goals overview document) 

1. Describe the mechanisms of absorption and scattering by which light interacts with matter. 

2. Describe how particle size, concentration and thickness of application affect how particles in a sus- 
pension scatter light. 

3. Explain how the phenomenon of seeing things in the world is a human visual response depending on 
how light interacts with objects. 

4. Evaluate the relative advantages (strong blockers, UVA protection) and disadvantages (possible car- 
cinogenic effects, not fully researched) of using nanoparticulate sunscreens. 



223 www.ckl2.org 



Table 2.22: All About Sunscreens Timeline 



Day 



Activity 



Time 



Materials 



Day 1 (50 min) 



Show All About Sun- 
screen PowerPoint 
Slides, using the em- 
bedded question slides 
and teacher's notes to 
start class discussion. 
(Embedded graph in- 
terpretation activity 
with student handout) 
Perform Demonstration 
associated with Power- 
Point Presentation (op- 
tional) 



50 min 



All About Sunscreen 
PowerPoint Slides & 
Teacher Notes 
Computer and projector 
Optional Demonstra- 
tion Materials: UV 
light, different kinds of 
paper currency. 
Copies of Light Re- 
by Three Sun- 
Student Hand- 



flection 

screens: 

out 

Light 

Three 



Reflection by 
Sunscreens: 



Teacher Answer Key 



Day 2 (35 min) 



Homework: Read Sun- 20 min 
screen Ingredients Ac- 
tivity: Student Instruc- 
tions & Worksheet 
Have students work 10 min 
in pairs to complete 
the data collection 
and fill in the chart 
in the Sunscreen In- 
gredients Activity: 
Student Instructions & 
Worksheet. Then have 
them continue to work 
in pairs to answer the 
discussion questions in 
the worksheet. 

Bring the class together 10 min 
as a whole to discuss 
questions 6-8. At the 
conclusion of the activ- 
ity hand out and discuss 
the summary of FDA 
approved sunscreens. 
Have students work in- 5 min 
dividually or in small 
groups to fill out the 
Reflecting on the Guid- 
ing Questions: Student 
Worksheet. 



Copies of Sunscreen 
Ingredients Activity: 
Student Instructions & 
Worksheet 

Different kinds of 
empty sunscreen bot- 
tles as listed in the 
Sunscreen Ingredients 
Activity: Teacher In- 
structions & Answer 
Key 



Summary of FDA Ap- 
proved Sunscreen Ingre- 
dients: Student Hand- 
out 



Copies of Reflecting on 
the Guiding Questions: 
Student Worksheet 



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224 



Table 2.22: (continued) 



Day 



Activity 



Time 



Materials 



Bring the class together 
to have students share 
their reflections with 
the class. 

This is also a good 
opportunity for you to 
address any miscon- 
ceptions or incorrect 
assumptions from stu- 
dents that you have 
identified in the unit up 
till now. 



10 min 



Reflecting on the Guid- 
ing Questions: Teacher 
Instructions & Answer 
Key 



Name 
Date 



Period 



Sunscreen Ingredients Activity: Teacher Instructions &; Answer Key 

This activity allows students to become familiar with the different ingredients used in sunscreens after 
learning about how different sunscreen ingredients work. After this activity you may want to give students 
the handout "Summary of FDA Approved Sunscreen Ingredients" to keep as a reference during the unit 
and the next time they go shopping for a sunscreen. 

Most of us (hopefully) apply sunscreen to protect us from the sun when we are going to be outside for a 
long time. But how many of us have ever stopped to read the bottle to see what we are putting on our 
bodies? What kinds of chemicals are used to block the sun rays? Do different sunscreens use different 
ingredients to block the sun? How might the different ingredients used affect us? In this activity you'll 
take a look at several sunscreens to see what we are putting on our bodies when we use these products. 

Materials 

• Five different bottles of sunscreen. 

To get a diverse group of sunscreens try to use more than one brand. Also see if you can find the following: 

• One sunscreen with a high SPF (30 - 50). 

• One sunscreen with a low SPF (5 - 15). 

• One sunscreen designed for skiers or surfers. 

• One sunscreen for sensitive skin or babies. 

• One sunscreen that has zinc oxide (ZnO) or titanium dioxide {TiO%) as an ingredient. Note: the 
proper scientific name for TiO^ is "titanium (IV) oxide ", but the older name "titanium dioxide " is 
more commonly used. 

This activity can be done as homework with a follow up class discussion or as an in-class activity. 
As Homework 



225 



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Ask your students to visit a local pharmacy or supermarket and do the assignment by looking at the 

sunscreens they find there. (There is no need for your students to buy any sunscreen.) 

You can ask also each student to research two or three sunscreens and then get together in groups 

in class to share their results and discuss the questions. 

Before assigning this as homework think about how easy / difficult it will be for your students to get 

to a pharmacy / supermarket and make sure to allow them enough time to do the assignment. 



In- Class 

• You will need to either develop your own library of sunscreen products or ask students to bring in 
products they have lying around at home. 

• It is best to use empty sunscreen bottles since the contents of the bottle are not needed for the 
activity and students may have unknown allergies to some sunscreen ingredients. You can then store 
the bottles for future use. 

• You will want to have a large enough collection and variety of sunscreens so that students aren't 
waiting to look at the bottles and that they have some choice in what sunscreens to look at. 

• It works best to place the sunscreens in stations and have students rotate through them in groups of 
2 or 3. 

Instructions 

Look at the back of one of the bottles. You should see a list of the "active ingredients" in the sunscreen. 
These are the ingredients that prevent sunlight from reaching your skin ("inactive ingredients" are added 
to influence the appearance, scent, texture and chemical stability of the sunscreen.) Also look to see what 
kind of protection the sunscreen claims to provide. Does it provide UVB protection? UVA protection? 
Does it claim to have "broad spectrum" protection? What is its SPF number? Does it make any other 
claims about its protection? Record your observations for each sunscreen in the data chart and then answer 
the questions that follow. 

Table 2.23: Data Chart 

Brand Active In- SPF UVB? UVA? Broad Price 

gredients Spectrum 

#2 
#3 

#4 
#5 



Questions 

Questions 1-5 ask students to review and synthesize the information they recorded from the different 
sunscreens, students should be able to answer these questions on their own based on the data they recorded. 

Questions 6-8 are deep thought questions that go beyond the information collected in this activity. 

1 . How many different active ingredients did most of the sunscreens have? 
Most sunscreens will have more than one ingredient. 

2. What were the most common active sunscreen ingredients you saw? Are these organic or inorganic 
ingredients? 



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Common sunscreen ingredients include: 

Homosalate, Octinoxate, Octisalate, Oxybenzone, Octocrylene (All organic) Zinc Oxide and Titanium 
Dioxide (Inorganic) are also common sunscreen ingredients. 

(also see FDA Approved Sunscreen Ingredient Resource for full list of ingredients) 

3. Did any of the sunscreens you looked at have active ingredients that were very different from the rest? 
If so, what were they? 

Avobezone (Parasol 1789) is sometimes added as because of it UVA blocking abilities. PABA (para 
aminobenozic acid) is infrequently used because it can irritate skin and stain clothes. 

Zinc Oxide and Titanium Dioxide is sometimes found in sunscreens designed for sensitive skin, babies and 
high SPF ski / surf sunscreens. 

4. Were you able to find a sunscreen with inorganic ingredients in it? If so, which one(s) contained them? 

Zinc Oxide and Titanium Dioxide (the only 2 FDA approved inorganic ingredients) are often found in 
sunscreens designed for sensitive skin, babies and high SPF ski / surf sunscreens. 

5. How many of your sunscreens claimed to have UVA protection? UVB protection? Broadband protec- 
tion? 

Most all sunscreens claim both UVB &; UVA protection, but since SPF only measures UVB protection, 
UVA protection claims currently do not need to be substantiated. 

Broadband protection is a general claim of protection for a wide spread of different wavelength of the 
electromagnetic spectrum bands. It is usually meant to imply that the sunscreen protects from both UVB 
(280 - 320 nm) and UVA (320 - 400 nm) radiation, however UVA protection is not yet regulated (see 
above), so this claim does not have to be substantiated. 

6. Why do you think that many sunscreens have more than one active ingredient? Why can't they just 
put in more of the "best" one? 

Different sunscreen ingredients prevent different wavelengths of light from reaching the skin. They block 
different parts of the UV spectrum. 

(A secondary reason is that high concentrations of chemicals on the skin can cause irritation, this is why 
when the FDA approves a sunscreen ingredient, it also lists the maximum concentration that can be used). 

7. You have just looked at a sample of the different chemicals you are putting on your skin when you use 
sunscreen. Does this raise any health concerns for you? If so, what are some of the things you might be 
concerned about and why? 

Irritation / allergies, chemicals getting absorbed by the body and having negative effects on the cells, 
possibility of getting in eyes, mouth or cuts where there is no skin barrier protection, photoactive chemicals 
can react with the sun to create free radicals which are known to help cause cancer. 

8. Where could you go to find out more information about possible health concerns? 

The FDA (Food and Drug Administration http://www.fda.gov/) regulates sunscreen ingredients in the 
U.S. and provides articles related to their use and safety. There are also many consumer watchgroups who 
provide information both online and in print. Most sunscreen companies do not publish information about 
health concerns associated with sunscreen. As with all research, it is important to always evaluate the 
credibility and potential bias of the author or organization presenting the information. 

You may want to give your students an assignment to search online for information about current health 
concerns related to nanoparticle use in sunscreens. 

All About Sunscreens 



227 www.ckl2.org 




What do Sunscreens Do? 




Figure 2.15 



• Sunscreens are designed to protect us by preventing UV rays from reaching our skin 

• But what does it mean to "block" UV rays? 
Light Blocking 

• Anytime light interacts with some material, 3 things can happen. The light can be transmitted, it 
can be reflected, or it can be absorbed 



• If we say that light is "blocked" it means that it is either absorbed or reflected by the material 
www.ckl2.org 228 



Total 

Incoming Light Absorbed Light 




Reflected Light 



Transmitted Light 



Figure 2.16 



Transmission 

Reflection 

-I- Absorption 

100% 



If we know that sunscreens block UV light from reaching our skin does that tell us whether 
they absorb or reflect the light? 




Figure 2.17 
Sometimes More Experiments Are Needed 

• Both absorption and reflection could explain how sunscreens keep UV light from reaching out skin 

— To figure out which mechanism is being used, we ran an experiment where we shine UV light 
on sunscreens and see if we can detect any reflection 

A Brief History of Sunscreens: The Beginning 

• First developed for soldiers in WWII (1940s) to absorb "sunburn causing rays" 



A Brief History of Sunscreens: The SPF Rating 

229 



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Total 

Incoming Light Absorbed Light 




Reflected Light 



We detected 
little UV light 
reflected - so 
r \f\J^ we know that 
Transmitted Light the sunscreens 
block via 
absorption 



Figure 2.18 




280 320 400 

Wavelength (nm) 







WWII soldiers 
in the sun 



The sunburn causing rays 
were labeled as UV-B 



Longer wavelengths in the 
UV range were called UV-A 



Figure 2.19 



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230 




30 



• <•-««* Mt 



Figure 2.20 



231 



www.ckl2.org 



• Sunscreens first developed to prevent sunburn 

— Ingredients were good UVB absorbers 

• SPF Number (Sunburn Protection Factor) 

— Measures the strength of UVB protection only 

— Higher SPF # = more protection from UVB 

— Doesn't tell you anything about protection from UVA 

A Brief History of Sunscreens: The UVA Problem 




Twenty different skin cancer lesions 

Figure 2.21 

• UVA rays have no immediate visible effects but cause serious long term damage 

— Cancer 

— Skin aging 

• Sunscreen makers working to find UVA absorbers 

• NEW: The FDA has just proposed a 4-star UVA rating to be included on sunscreen labels! 

Low* • •• Med* • •• High* • •• Highest* • •• 

How do you know if your sunscreen is a good UVA blocker? 

Know Your Sunscreen: Look at the Ingredients 



UV absorbing agents suspended in a lotion 

— "Colloidal suspension" 
Lotion has "inactive ingredients" 

— Don't interact w/ UV light 



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232 




Figure 2.22 




] = Lotion =Active Ingredients 



Figure 2.23 



233 



www.ckl2.org 



UV absorbing agents are "active ingredients" 

— Usually have more than one kind present 
Two kinds of active ingredients 

— Organic ingredients and inorganic ingredients 



Table 2.24: Sunscreen Ingredients Overview 



Organic Ingredients Inorganic Ingredients 



Atoms Involved Carbon, Hydrogen, Oxygen, Ni- Zinc, Titanium, Oxygen 

trogen 
Structure (not drawn to scale) Individual molecule 

title 



www.ckl2.org 234 



Table 2.24: (continued) 



Organic Ingredients Inorganic Ingredients 



i3» 



Absorb specific bands of UV light Absorb all UV with A < critical 

value 




•x 




tfikt 



*'&&* 

<**\ J+'' 



UV Blocking 

Appearance Clear Large clusters = White 

Small clusters = Clear 



Organic Ingredients: The Basics 

• Organic = Carbon Compounds 

— H,0 & N atoms often involved 



235 www.ckl2.org 



Octyl methoxycinnamate (C 18 H 26 3 ) 
an organic sunscreen ingredient 




Figure 2.24 



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236 



Structure 



Covalent bonds 

Exist as individual molecules 



• Size 

— Molecular formula determines size (states the number and type of atoms in the molecule) 

— Typically a molecule measures a few to several dozen A (< 10 nm) 

Organic Ingredients: UV Blocking 

Organic Sunscreen Ingredients can absorb UV rays 



incoming 
UV radiation 



Outgoing 
IR radiation 






Excitad 

Moitcult 




Figure 2.25 

1. Molecules capture energy from the sun's UV rays 

2. The energy give the molecule thermal motion (vibrations and rotations) 

3. The energy is re-emitted as harmless long wave IR 

Organic Ingredients: Absorption Range 

• Organic molecules only absorb UV rays whose energy matches the difference between the molecule's 
energy levels 

— Different kinds of molecules have different peaks and ranges of absorption 

— Using more than one kind of ingredient (molecule) gives broader protection 

Organic Ingredients: Absorbing UVA / UVB 

• Most organic ingredients that are currently used were selected because they absorb UVB rays 

— The FDA has approved 15 organic ingredients 

— 13 of these primarily block UVB rays 

• Sunscreen makers are working to develop organic ingredients that absorb UVA rays 

— Avobenzone (also known as Parasol 1789) is a good FDA approved UVA absorber 



237 



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Orr S.mtrrMn lngr»di»n< 



T«« Si nirrMn IngrrrtirnM 




JOS MC SCO SCO 403 

W.v.l.nglh (n«) 




»M ICC 3tfl 403 

W«val«ngth |n«0 







so» »i* ice Jto 

W«vil*nglh (nn) 



Figure 2.26 




Figure 2.27 



-Breaking News- 



Ecamsule (Mexoryl SX) is a new sunscreen ingredient designed to absorb UVA rays 
— It is the first new sunscreen ingredient approved by the FDA since 1988 



?D0 

600-1 

500 

» »XH 

200 

100 

00 




-i 1 1 1 1 1 r 

^ ^ W 8 k S S 



ecarou* 2% 
-- ottocrylerw 1 0* ' avob«m:one 2% 



WAVTLCNJGTI | i , 



Figure 2.28 



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238 



How are inorganic sunscreen ingredients different from organic ones? 
How might this affect the way they absorb UV light? 
Inorganic Ingredients: The Basics 



Detail of the ions in 
one cluster 




Group of Ti0 2 particles 

Figure 2.29 



• Atoms Involved 

— Zinc or Titanium 

— Oxygen 

• Structure 

— Ionic attraction 

— Cluster of ions 

— Formula unit doesn't dictate size 

• Size 

— Varies with # of ions in cluster 

— Typically ~ 10 nm - 300 nm 

Inorganic Ingredients: Cluster Size 

Inorganic ingredients come in different cluster sizes (sometimes called "particles") 

• Different number of ions can cluster together 

239 www.ckl2.org 



Must be a multiple of the formula unit 

— ZnO always has equal numbers of Zn and atoms 

— T1O2 always has twice as many as Ti atoms 




-100 nm 



Two 

Ti0 2 particles 



Figure 2.30 




-200 nm 



Inorganic Ingredients: UV Blocking 



Inorganic Compound Absorption 
1.0 



o.c 



200 250 300 350 400 

Way elength (nm) 



Figure 2.31 

Inorganic Sunscreen Ingredients can also absorb UV rays 

— But a different structure leads to a different absorption mechanism 



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240 



— Absorb consistently through whole UV range up to ~ 380 nm 

— How is the absorption pattern different than for organics? 

If inorganic sunscreen ingredients block UVA light so well, why doesn't everybody use them? 




Figure 2.32 



Appearance Matters 




Figure 2.33 



Traditional inorganic sunscreens appear white on our skin 

241 



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• Many people don't like how this looks, so they don't use sunscreen with inorganic ingredients 

• Of the people who do use them, most apply too little to get full protection 

Why Do They Appear White? I 




Figure 2.34 



• Traditional ZnO and T1O2 clusters are large 

- (> 200 nm) 

• Large clusters can scatter light in many different directions 

• Maximum scattering occurs for wavelengths twice as large as the cluster 

- A > 400 nm 

- This is visible light! 

Why Do They Appear White? II 

Light eventually goes in one of two directions: 

1. Back the way it came (back scattering) 

• Back-scattered light is reflected 

2. Forwards in the same general direction it was moving (front scattering) 

• Front-scattered light is transmitted 
Why Do They Appear White? Ill 

• When reflected visible light of all colors reaches our eyes, the sunscreen appears white 
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Back Scattering 



- 



o 

o 



"o o \ ?/ ? ° 



^\ 



I - nl Scattering 



Figure 2.35 

• This is very different from what happens when sunlight is reflected off our skin directly 

— Green/blue rays absorbed 

— Only red/brown/yellow rays reflected 

Why don't organic sunscreen ingredients scatter visible light? 

Organic Sunscreen Molecules are Too Small to Scatter Visible Light 

What could we do to inorganic clusters to prevent them from scattering visible light? 

Nanosized Inorganic Clusters 

• Maximum scattering occurs for wavelengths twice as large as the clusters 

— Make the clusters smaller (100 nm or less) and they won't scatter visible light 

Nano- Sunscreen Appears Clear 
Let's Look at Some Real Data... 

• Three sunscreens were tested for reflection (backscattering) with different wavelengths of light 

— One contains nanosized inorganic ingredients 

— One contains traditional inorganic ingredients 

— One contains organic ingredients 

• Answer the following questions for each sunscreen: 
1. Will it appear white or clear on your skin? 



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Figure 2.36 



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244 




Figure 2.37 




200 nm Ti0 2 particle 
(Inorganic) 



Methoxycinnamate (<10 nm) 
(Organic) 



Figure 2.38 




I 




Figure 2.39 



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Figure 2.40 



Nanosized ZnO 
particles 



Large ZnO 
particles 




Figure 2.41 



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246 



2. What size (approximately) are the molecules / clusters? 

3. Can we tell how good a UV blocker it is from this graph? Why/ why not? 

4. Which one of the sunscreens is it? How do you know? 

Light Reflected by Three Sunscreens 



— - Sunscreen 1 



■ Sunscreen 2 



Sunscreen 3 



■:d 



;o 



EL 



o JO 



■o 



?:o si: ?:o ss: ?« :-:: ?so s:: ?;c sw -ijo -i: 42c -:: -s-c i?: 4ec --a 4.-:: 4:0 50: 



Wavelength of Light 



Figure 2.42 



Table 2.25: In Summary I 



Organic Ingredients Inorganic Ingredients (Nan inorganic Ingredients(Large) 

Structure Individual molecule Cluster ~ 100 nm in di- Cluster > 200 nm in di- 
ameter ameter 
Interaction w/ UV light Absorb specific A of UV Absorb all UV < critical Absorb all UV < critical 

light A A 

Absorption Range Parts of UVA or UVB Broad spectrum, both Broad spectrum, both 

spectrum UVA and UVB UVA and UVB 

Interaction w/Vis light None None Scattering 

Appearance Clear Clear White 



In Summary II 



Nanoparticle sunscreen ingredients are small inorganic clusters that: 

— Provide good UV protection by absorbing most UVB and UVA light 

— Appear clear on our skin because they are too small to scatter visible light 



Essential Questions: Time for Answers 

1. What are the most important factors to consider in choosing a sunscreen? 

2. How do you know if a sunscreen has "nano" ingredients? 

3. How do "nano" sunscreen ingredients differ from other ingredients currently used in sunscreens? 



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Figure 2.43 

Teacher Notes 

Overview 

This series of slides discusses the basics of sunscreens including their history, types, mechanism for blocking 
UV light (absorption), appearance (due to scattering) and challenges to providing effective protection. The 
final slide asks students to use what they've learned to answer the three driving questions for the unit. 

Slide 14 includes an optional demo that shows how selective absorption of UV light by certain chemicals 
used in printing money is serves as an anti-counterfeiting measure. If you choose to do this demo you will 
need: 

• One or more UV lights of any size (several options are available from Educational Innovations at 
www . teachersour ce .com) 

• Different kinds of paper currency (these must be relatively recently printed; Euros and Canadian 
bills work particularly well) 

Slide 1: Title Slide 

Slide 2: What do Sunscreens Do? 

This slide is designed to get students thinking about how sunscreens protect our skin. Have students 
brainstorm ideas about what might happen to the UV rays when they encounter the sunscreen. Ask them 
how they could test their ideas to see if they are correct. 

Slide 3: Light Blocking 

The T + R + A = 100% equation is based on the conservation of energy. All incoming light (energy) must 
be accounted for. It either passes through the material, is sent back in the direction from which it came 
or is absorbed by the material. 

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Analogy: The R + T + A — 100% equation can be thought of in terms of baseball. When a pitcher throws 
the ball towards the batter, three things can happen. The batter can hit the ball (reflection), the catcher 
can catch the ball (absorption) , or the ball can pass by both of them (transmission) . 

Slide 4: If we know that sunscreens block UV light from reaching our skin does that tell us 
whether they absorb or reflect the light? (Question Slide) 

Have your students brainstorm ideas about we could figure out what happens to the light. You may need 
to remind them that the question asks about UV light (which is not visible to the human eye). Assuming 
we had a UV light detector, where would we want to put it and what would we expect it to measure for 
each possible scenario (absorption and reflection)? 

Slide 5: Sometime More Experiments Are Needed 

A key point of this slide is that there are often multiple valid theoretical explanations for experimental 
data; to find out which works best, additional experiments are required. 

For example, it is well known that sunscreens "block" UV light, but this could be viably explained by 
either absorption or reflection. 

To find out which explanation was a better fit for the "blocking" phenomenon, we conducted an experiment 
in which we prepared a series of glass slides covered with sunscreens. We shone UV light on the sunscreens 
and placed UV light detectors both on the other side of the slide (to measure transmitted light) and next to 
the original light source (to measure reflected light). Little reflected or transmitted UV light was detected, 
so we can infer from T + R + A = 100% that the sunscreen is absorbing the UV light. 

Note that it is often possible to engineer useful materials with an incomplete understanding of their 
properties. In this example we can design sunscreens that provide effective protection against UV light 
without knowing whether they do so via absorption or reflection. 

Slide 6: A Brief History of Sunscreens: The Beginning 

Sunscreens were developed to meet a specific and concrete need: prevent soldiers from burning when 
spending long hours in the sun. Scientists applied their knowledge of how light interacts with certain 
chemicals to develop products to meet this need. 

The division of the continuous UV spectrum into UVA and UVB categories is somewhat arbitrary. The 
UVB range is talked about as starting at around 280 - 290 nm at the lower end and ending around 
310 - 320 nm at the upper end. 

Slide 7: A Brief History of Sunscreens: The SPF Rating 

SPF (Sunscreen Protection Factor) values are based on an "in-vivo" test (done on human volunteers) that 
measures the redness of sunscreen- applied skin after a certain amount of sun exposure. 

SPF used to be thought of a multiplier that can be applied to the time taken to burn, but this is not done 
anymore because there are so many individual differences and other variables that change this equation 
(skin type, time of day, amount applied, environment, etc.) 

The FDA recommends always using sunscreens with an SPF of at least 15 and not using sunscreen as a 
reason to stay out in the sun longer. Remind students that no sunscreen can prevent all possible skin 
damage. 

Common Student Question: Is it true that sunscreens above SPF 30 don't provide any extra protection? 

Answer: No, this is not true. However, since SPF is not based on a linear scale, a sunscreen with an SPF 
of 40 does not provide twice as much protection as a sunscreen with an SPF of 20. Even though you don't 
get double the protection, you do get some additional protection and so there is added value in using SPFs 
above 30. 

In the past the FDA only certified SPFs up to 30 but didn't confirm the reliability of higher claims by 

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sunscreen manufacturers. Recently, due to improvement in testing procedures, the FDA had proposed 
certifying results up to and SPF of 50. 

Slide 8: A Brief History of Sunscreens: The UVA Problem 

Since there is no immediate visible effect, it is relatively recently that we have come to understand the 
dangers of UVA rays. In August 2007, the FDA proposed a UVA rating to be included on sunscreen labels; 
as of December 2007, the proposal was still under discussion. If the FDA proposal is passed, sunscreen 
manufacturers will have 18 months to comply with the new labeling requirements. 

Creating a rating for UVA protection has been difficult for two reasons: 

1. Since UVA radiation does not lead to immediate visible changes in the skin (such as redness) what 
should be the outcome measure? Is it valid to do an "in-vitro" (in a lab and not on a human) test? 
( The FDA proposal includes both) 

2. How should the UVA protection level be communicated to consumers without creating confusion 
(with the SPF and how to compare / balance the two ratings)? (The FDA proposal uses a 4-star 
system) 

Creating a UVA blocking rating is important since without immediate harmful effects, people are not likely 
to realize that they have not been using enough protection until serious long term harm has occurred. 

Slide 9: How do you know if your sunscreen is a good UVA blocker? (Question Slide) 

Have your students brainstorm ideas about ways to tell if a sunscreen is a good UVA blocker. 

Slide 10: Know Your Sunscreen: Look at the Ingredients 

"Formulating" a sunscreen is the art of combing active and inactive ingredients together into a stable cream 
or gel product. One of the important challenges here is creating a stable suspension with even ingredient 
distribution. If the active ingredients clump together in large groups then the sunscreen provides strong 
protection in some areas and little protection in others. 

Analogy: Students may be familiar with the suspension issue as it relates to paint. If paint has been 
sitting for a while and it is used directly, a very uneven color is produced. This is why we stir (or shake) 
paint before using in order to re-suspend the particles. 

Another issue in sunscreen formulation is trying to create a product that customers will want to buy and 
use. Qualities such as smell, consistency and ease of rubbing into the skin all play a role in whether or not 
a sunscreen will be used and whether it will be used in sufficient quantity. 

Slide 11: Sunscreen Ingredients Overview 

This slide is an advance organizer for the content of the rest of the slide set. You may wish to give your 
students the Overview of Sunscreen Ingredients: Student Handout at this point to refer to during the rest 
of the presentation. 

You do not need to discuss the details of each cell at this point in the presentation, simply point out that 
organic and inorganic ingredients have several different properties that will be discussed. All of the content 
of the table is explained in detail in the following slides. 

Slide 12: Organic Ingredients: The Basics 

The full name of the compound shown is octyl methoxycinnamate (octyl refer to the eight carbon hy- 
drocarbon tail shown on the right side of the molecule) but it is commonly referred to as octinoxate or 
OMC. 

Slide 13: Organic Ingredients: UV Blocking 

When a molecule absorbs light, energy is converted from an electromagnetic form to a mechanical one (in 

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the form of molecular vibrations and rotations). Because of the relationship between molecular motion 
and heat, this is often referred to as thermal energy. 

The process of releasing the absorbed energy is called relaxation. While atoms which have absorbed 
light simply re-emit light of the same wavelength/energy, molecules have multiple pathways available for 
releasing the energy. Because of the many vibrational and rotational modes available, there are many 
choices for how to relax. Since these require smaller energy transitions than releasing the energy all at 
once, they provide an easier pathway for relaxation - this is why the energy absorbed from the UV light 
is released as harmless (low energy) IR radiation. 

Slide 14: Organic Ingredients: Absorption Range 

Light absorption by molecules is similar to the emission of light by atoms with three key differences: 

• Light is captured instead of released. 

• Molecules absorb broader bands of wavelengths than atoms because there are multiple vibrational 
and rotational modes to which they can transition (for more details on molecular absorption concepts, 
see the Lesson 3 PPT and teacher notes). 

• There are multiple pathways for relaxation - the light emitted does not have to be the same wave- 
length as the light absorbed. 

Different molecules have different peak absorption wavelengths, different ranges of absorption and differ- 
ences in how quickly absorption drops off ("fat" curves as compared to "skinny" ones). It is important 
to realize that even within a molecule's absorption range, it does not absorb evenly and absorption at 
the ends of the range is usually low. For example, octyl methoxycinnamate has an absorption range of 
295 - 350 nm, but we would not expect it to be a strong absorber of light with a wavelength of 295 nm. 

UV Absorption Demonstration: As one effort to prevent the circulation of counterfeit currency, bills 
are often printed with special chemicals that absorb specific wavelengths of UV light (this occurs because 
the energy of these UV rays matches the difference between the molecule's energy levels). When one of 
these bills is held under a UV light, these molecules absorb the UV light and reemit purple light in the 
visible spectrum that we can see (note that that the remitted light is not UV light which is not visible 
to the human eye). You can demonstrate this effect for your students by turning off the classroom lights 
and shining a UV light on different kinds of bills and watching the printed designs appear (these must be 
relatively recently printed; Euros and Canadian bills have particularly interesting designs). If you have two 
UV lights of different wavelengths, you may even be able to see two different designs due to the selective 
absorption of the different molecules used in the printing. 

Slide 15: Organic Ingredients: Absorbing UVA / UVB 

Many organic ingredients block "shortwave" UVA light (also called UVA 2 light and ranging from ~ 320 
to 340 nm) but not "longwave" UVA light also called UVA 1 light and ranging from ~ 340 to 400 nm). 
Up till 2006, avobenzone was the only organic ingredient currently approved by the FDA that is a good 
blocker of longwave UVA light. 

Slide 16: Breaking News 

In the summer of 2006, the FDA approved Ecamsule (Mexoryl SX), a new sunscreen ingredient designed 
to absorb UVA rays. One benefit of this ingredient is that it is photostable (many sunscreens are degraded 
by the sun), but since it is water soluble, it does not provide protection in the water. 

This is the first new ingredient to be approved by the FDA since 1998; however it has been approved 
in Europe since 1991. There is a great deal of pressure on the FDA to approve several other sunscreen 
ingredients that are already approved in Europe. 

Graph Q & A for students: 

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What does the y-axis shows? (% absorption) 

What kinds of wavelengths does this ingredient absorb? (UVA up to ~ 360 nm) 

Is this an organic ingredient? (Yes) 

How do you know? (Molecular structure with carbon, hydrogen, and nitrogen) 



Slide 17: How are inorganic sunscreen ingredients different from organic ones? How might 
this affect the way they block UV light? (Question Slide) 

Have your students brainstorm how inorganic sunscreens might be different from organic ones and how 
this might affect the way they block UV light. 

Slide 18: Inorganic Ingredients: The Basics 

Inorganic compounds are described by a formula unit instead of a molecular formula. The big difference 
is that while a molecular formula tells you exactly how many of each kind of atom are bonded together 
in a molecule; the formula unit only tells you the ratio between the atoms. Thus while all molecules of 
an organic substance will have exactly the same number of atoms involved (and thus be the same size), 
inorganic clusters can be of any size as long as they have the correct ratio between atoms. This occurs 
because inorganic substances are held together by ionic, not covalent bonds. 

You may want to review some of the basics of bonding in inorganic compounds (electrostatic attraction 
between ions) as opposed to bonding in organic molecules (electron sharing via covalent bonds) with your 
students here. 

Slide 19: Inorganic Ingredients: Cluster Size 

Note: the proper scientific name for TiOi is "titanium (IV) oxide", but the older name "titanium dioxide" 
is more commonly used. 

This slide is a re-emphasizes the difference between a molecular formula and the formula unit of an inorganic 
substance. While the molecular formula indicates the actual number of atoms that combine together to 
form a molecule, the formula unit indicates the ratio of atoms that combine together to form an inorganic 
compound. Molecules are always the same size whereas inorganic compounds can vary in the number of 
atoms involved and thus the size of the cluster. 

Common Confusion: Inorganic compound clusters are often referred to informally as "particles". Stu- 
dents often confuse this use of the word particle with the reference to the sub-atomic particles (proton, 
electrons and neutrons) or with reference to a molecule being an example of a particle. 

Slide 20: Inorganic Ingredients: UV Blocking 

When an inorganic compound absorbs light, energy is converted from an electromagnetic form to a me- 
chanical one (kinetic energy of electrons). The excited electrons use this kinetic energy to "escape" the 
attraction of the positively charged nuclei and roam more freely around the cluster. 

Because there are so many more atoms involved in an inorganic compound than in a molecule, there are 
also many more different energy values that electrons can have (students can think of these loosely as how 
"free" the electrons are to move about the cluster; how far from their original position they can roam). 
The greater number of possible energy states means that a greater range of wavelengths of UV light can 
be absorbed leading to the broader absorption spectrum shown in the graph. 

Slide 21: If inorganic sunscreens ingredients block UVA light so well, why doesn't everybody 
use them? (Question Slide) 

Have your students brainstorm reasons why sunscreen manufacturers and consumers might not want to 
use inorganic sunscreen ingredients. 

Slide 22: Appearance Matters 

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One of the major reasons that people have not used inorganic ingredients in the past is because of their 
appearance. Before we knew how dangerous UVA rays were, sunscreens with organic ingredients seemed 
to be doing a good job (since they do block UVB rays). 

Applying too little sunscreen is very dangerous because this reduces a sunscreen's blocking ability while 
still giving you the impression that you are protected. In this situation people are more likely to stay out 
in the sun longer and then get burned. 

Slide 23: Why Do They Appear White? I 

Scattering is a physical process that depends on cluster size, the index of refraction of the cluster substance 
and the index of refraction of the suspension medium. No energy transformations occur during scattering 
(like they do in absorption); energy is simply redirected in multiple directions. The wavelengths (and 
energy) of light coming in and going out are always the same. 

Maximum scattering occurs when the wavelength is twice as large as the cluster size. Since traditional 
inorganic sunscreen ingredients have diameter > 200 nm, they scatter light which is > 400 nm in diameter 
- this is in the visible spectrum. 

Slide 24: Why Do They Appear White? II 

Multiple scattering is a phenomenon of colloids (suspended clusters). When light is scattered, at the micro 
level it goes in many directions. At the macro level, it eventually either goes back the way it came or 
forwards in the same general direction it was moving. These are known as back- and front- scattering and 
they contribute to reflection and transmission respectively. 

Note that the formula presented earlier (Reflection + Transmission + Absorption = 100%) still holds. 
Scattering simply contributes to the "reflection" and "transmission" parts of the equation. (For more 
details on scattering concepts, see the Lesson 4 PPT and teacher notes). 

Slide 25: Why Do They Appear White? Ill 

The scattering of visible light by ZnO and T1O2 is the cause of the thick white color seen in older sunscreens. 
When the different colors of visible light are scattered up and away by the sunscreen, they reach our eyes. 
Since the combination of the visible spectrum appears white to our eyes, the sunscreen appears white. 

Depending on your students' backgrounds, you may want to review how white light is a combination of all 
colors of light. 

You may also want to discuss how the pigment in our skin selectively absorbs some colors (wavelengths) of 
visible light, while reflecting others. This is what usually gives our skin its characteristics color. Different 
pigments (molecules) absorb different wavelengths; this is why different people have different color skin. 

Slide 26: Why don't organic sunscreen ingredients scatter visible light? (Question Slide) 

Have your students brainstorm reasons why organic sunscreen ingredients don't scatter visible light. 

Slide 27: Organic Sunscreen Molecules are Too Small to Scatter Visible Light 

Traditional inorganic clusters are usually 200 nm or larger, causing scattering in the visible range (400 - 
700 nm). Organic sunscreen molecules are smaller than 10 nm (usually 1-20 Angstroms) and thus do not 
scatter in the visible range. 

You may want to talk about how while the individual organic sunscreen molecules are very small compared 
to inorganic sunscreen clusters (many formula units ionically bonded together creating a large cluster) and 
the wavelengths of visible light, they are big compared to many of the simple molecules that students are 
used to studying, such as water or hydrochloric acid. 

How big or small something seems is relative to what you are comparing it to. In this case, we are 
comparing sunscreen ingredients with the size of the wavelength of light. 

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Slide 28: What could we do to inorganic clusters to prevent them from scattering visible 
light? (Question Slide) 

Have your students brainstorm what we could do to inorganic clusters to prevent them from scattering 
light. If students say "make them smaller", ask them how small the clusters would need to be in order to 
not scatter visible light. 

Slide 29: Nanosized Inorganic Clusters 

When visible light is not scattered by the clusters, it passes through the sunscreen and is reflected by our 
skin (blue and green rays are absorbed by pigments in the skin and the red, yellow and orange rays are 
reflected to our eyes giving skin its characteristic color). 

Changing the size of the cluster does not affect absorption since this depends on the energy levels in the 
substance which are primarily determined by the substance's chemical identity. 

Discussion Question for Students: Is it good or necessary to block visible light from reaching our skin? 

Answer: Visible light has less energy than UVA light and is not currently thought to do any harm to our 
skin thus there is no need to block it. Think about human vision: visible light directly enters our eyes on 
a regular basis without causing any harm. 

If you are not planning on doing Lesson 4: You may want to demo the sunscreen animations for your 
class at this point. The animations are available at http : //nanosense . org/activities/clearsunscreen/ 
index.html and are explained in the Sunscreens & Sunlight Animations: Teacher Instructions & Answer 
Key in Lesson 4. 

Slide 30: Nano-Sunscreen Appears Clear 

This slide shows the difference in appearance between traditional inorganic and nanosunscreens. 

Slide 31: Let's Look at Some Real Data... 

At this point you should hand out the Light Reflection by Three Sunscreens: Student Worksheet. You can 
either have students work on it in groups or proceed to the next slide and work through the questions as 
a whole class. 

Slide 32: Light Scattering by Three Sunscreens 

The following answers are also presented in chart form in the Light Reflection by Three Sunscreens: Teacher 
Answer Key. 

Sunscreen 1 

Appearance 

• No scattering in the visible range 

• Sunscreen appears clear on the skin. 



Size 



• Since no scattering seen, it is not possible to estimate the size of the molecule from the information 
in the graph. 

UV Blocking 

• The graph shows very little reflection in the UV range, however, this doesn't tell us anything because 
absorption is the main blocking mechanism for UV. 

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We would need an absorption or transmission graph in order to determine the UV blocking ability 
of the sunscreens. 
T +R+A = 1 



Identity 



Virtually no scattering in the visible range indicates organic ingredients. 

Because organic molecules are small compared to the wavelengths of light used, almost no scattering 

in the visible range occurs and the line is basically flat. 

This sunscreen contains the organic ingredients octinoxate (shown on slides 9 & 10) and oxybenzone. 

(The sunscreen is Walgreens SPF 15). 



Sunscreen 2 

Appearance 



Very limited scattering in the visible range 
Sunscreen appears clear on the skin. 



Size 



• The sharp drop in the curve at 380 nm is actually due to absorption (if all the light is getting 
absorbed, it can't be scattered) so we cannot know the exact size of the cluster. 

• We only know that the curve would have peaked below 380 nm, so the cluster size is smaller than 
190 nm. 

UV Blocking 

• See general explanation under Sunscreen 1. 
Identity 

• Low amounts of scattering in the visible range, indicates inorganic ingredients with nanosized clusters. 

• Because nanosized clusters are less than half the size of the wavelengths of light used, limited scat- 
tering in the visible range occurs. 

• This sunscreen contains nanosized zinc oxide. 

• (The sunscreen is Skin Ceuticals SPF 30). 

Sunscreen 3 

Appearance 

• Significant scattering in the visible range. 

• Sunscreen appears white on the skin. 



Size 



Significant scattering in the visible range. 
Sunscreen appears white on the skin. 



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UV Blocking 

• See general explanation under Sunscreen 1. 
Identity 

• Significant amounts of scattering in the visible range indicates inorganic ingredients with large clusters 
size. 

• Because traditional inorganic ingredient clusters are about half the size of the wavelengths of light 
used, a great deal of scattering in the visible range occurs. 

• This sunscreen contains traditional titanium dioxide. 

• (The sunscreen is Bullfrog SPF 45). 

Slide 33: In Summary I 

If you have not yet given your students the Overview of Sunscreen Ingredients: Student Handout, do so 
now. Use the handout to review the similarities and differences between the three kinds of ingredients. 

Key Similarities &: Differences: 

• Both kinds of inorganic ingredients have the same atoms, structure and UV absorption 

• Nano-inorganic clusters are much smaller than the cluster size of traditional inorganic ingredients, 
thus do not scatter visible light, thus are clear. 

Slide 34: In Summary II 

The big benefit of nano-sunscreen ingredients is that they combine UVA blocking power with an acceptable 
appearance. 

Slide 35: Essential Questions: Time for Answers 

Hand out the Reflecting on the Guiding Questions: Student Worksheet and have students work in pairs 
to answer it. You may also want to review the questions with the class as a whole. 

Light Reflection by Three Sunscreens: Teacher Answer Key 

Introduction 

Three sunscreens were tested for reflection (back-scattering) with different wavelengths of light: 

• One contains nanosized inorganic ingredients 

• One contains traditional inorganic ingredients 

• One contains organic ingredients 

A graph was created to show the percent of light reflected by each sunscreen at different wavelengths and 
is included in this packet. 

Instructions 

Use the graph to answer the following questions for each sunscreen in the chart on the next page: 

1. Will it appear white or clear on your skin? How do you know? 

2. What size (approximately) are the molecules / clusters? 

3. Can we tell how good a UV blocker it is from this graph? Why/ why not? 

4. Which one of the sunscreens is it? How do you know? 



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Table 2.26: Light Reflection by Three Sunscreens Chart 



Appearance 



Size 



UV Blocking 



Identity (w/ rea- 
son) 



#1 



No scattering in 
the visible range 
Sunscreen appears 
clear on the skin. 



#2 



Very limited scat- 
tering in the visi- 
ble range 

Sunscreen appears 
clear on the skin. 



Since no scatter- 
ing seen, it is not 
possible to esti- 
mate the size of 
the molecule from 
the information in 
the graph. 



The sharp drop 
in the curve at 
380 nm is actually 
due to absorption 
(if all the light is 
getting absorbed, 
it can't be scat- 
tered) so we can- 
not know the exact 
size of the cluster. 
We only know 
that the curve 
would have peaked 
below 380 nm, so 
the cluster size 
is smaller than 
190 nm. 



The graph shows 
very little reflec- 
tion in the UV 
range, however, 
this doesn't tell us 
anything because 
absorption is the 
main blocking 

mechanism for 

UV. 

We would need 
an absorption 

or transmission 
graph in order to 
determine the UV 
blocking ability 
of the sunscreens. 
T +R+A = 1 



See above. 



Virtually no 

scattering in the 
visible range in- 
dicates organic 
ingredients. 
Because organic 
molecules are 

small compared to 
the wavelengths of 
light used, almost 
no scattering in 
the visible range 
occurs and the line 
is basically flat. 
This sunscreen 
contains the or- 
ganic ingredients 
octinoxate (shown 
on slides 9 & 10) 
and oxybenzone. 
(The sunscreen is 
Walgreens SPF 
15). 

Low amounts 

of scattering in 
the visible range, 
indicates inorganic 
ingredients with 
nanosized clusters. 
Because nanosized 
clusters are less 
than half the size 
of the wavelengths 
of light used, lim- 
ited scattering in 
the visible range 
occurs. 

This sunscreen 
contains nanosized 
zinc oxide. 
(The sunscreen 
is Skin Ceuticals 
SPF 30) 



257 



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Table 2.26: (continued) 



Appearance 



Size 



UV Blocking 



Identity (w/ rea- 
son) 



#3 



Significant catter- 
ing in the visible 
range. 

Sunscreen appears 
white on the skin. 



Because the graph 
peaks around 

450 nm, we would 
estimate the clus- 
ter size to be 
about 225 nm. 



See above. 



Significant 
amounts of scat- 
tering in the 
visible range in- 
dicates inorganic 
ingredients with 
large clusters size. 
Because tradi- 

tional inorganic 
ingredient clusters 
are about half the 
size of the wave- 
lengths of light 
used, a great deal 
of scattering in 
the visible range 
occurs. 

This sunscreen 
contains tradi- 

tional titanium 
dioxide. 

(The sunscreen is 
Bullfrog SPF 45). 



Light Reflected by Three Sunscreens 



— -Sunscreen 1 



Sunscreen 2 



Suaoan 3 




300 310 320 330 340 350 M0 370 M0 3SC 400 410 420 430 +40 450 460 470 490 460 500 

Wavelength of Light 



Figure 2.44 



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258 



Reflecting on the Guiding Questions: Teacher Instructions & Answer 
Key 

You may want to have your students keep these in a folder to use at the end of the unit, or collect them to 
see how your students' thinking is progressing. You can also have a group discussion about what students 
learned from the activity that helps them answer the guiding questions. 

Discussion Idea: 

For each "What I still want to know" section, have students share their ideas and discuss whether their 
questions are scientific ones or questions of another sort. Scientific questions are questions about how the 
natural world operates that can be answered through empirical experiments. Other kinds of questions 
might be ethical in nature (e.g. do friends have a responsibility to persuade friends to use sunscreen?) or 
policy questions (e.g. should the FDA endorse the most effective sunscreens?). 

Think about the activities you just completed. What did you learn that will help you answer the guiding 
questions? Jot down your notes in the spaces below. 

1. What are the most important factors to consider in choosing a sunscreen? 
What I learned in this activity: 

Possible Answers: 

It is important to choose a sunscreen that provides good protection against both UVA and UVB. 

A sunscreen's SPF number tells us how well the sunscreen protects against UVB rays. 

Right now there is no regulated measure of UVA protection. Sunscreen labels that claim UVA or "broad- 
band" protection may or may not actually protect against all UVA light. 

Until the new FDA UVA rating is approved, the only way to tell how well a sunscreen protects against UVA 
rays is by looking at the ingredients. Avobenzone and Ecamsule are two organic ingredients that provide 
protection from some of the UVA range. Zinc Oxide and Titanium Dioxide are two inorganic ingredients 
that provide protection from almost the whole UVA range. 

It is also important to choose a sunscreen that we like in terms of appearance and smell to make sure that 
we use enough of it to be effective. 

What I still want to know: 

2. How do you know if a sunscreen has "nano" ingredients? 
What I learned in this activity: 

Possible Answers: 

"Nano" ingredients are smaller versions of traditional inorganic ingredients that go on clear. If a sunscreen 
contains Zinc Oxide or Titanium Dioxide, but appears clear on our skin, then it likely contains nanoparticles 
of ZnO or TiOi- 

What I still want to know: 

3. How do "nano" sunscreen ingredients differ from most other ingredients currently used in sunscreens? 
What I learned in this activity: 

Possible Answers: 

Most ingredients currently used in sunscreens are organic ingredients. These are individual molecules that 
absorb narrow bands of the UVA or UVB spectrum. 

"Nano" sunscreen ingredients are inorganic and absorb almost the whole UV spectrum. 

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"Nano" sunscreen ingredients are inorganic and very similar to traditional inorganic ingredients (large ZnO 
and TiOi clusters) - they are made up of the same kinds of atoms and have the same formula unit, thus 
they absorb strongly in both the UVA and UVB range up to their cutoff wavelength: 380 nm {ZnO) or 
365 nm (Ti0 2 ). 

What I still want to know: 

How Sunscreens Block: The Absorption of UV Light 

Contents 

• How Sunscreens Block: The Absorption of UV Light: Teacher Lesson Plan 

• How Sunscreens Block: The Absorption of UV Light: PowerPoint Slides and Teacher Notes 

• Reflecting on the Guiding Questions: Teacher Instructions & Answer Key 

Teacher Lesson Plan 

Orientation 

This lesson introduces students to the core science behind sunscreen absorption of UV light. This is 
an advanced topic that requires students to have a background in atomic energy levels, absorption and 
emission processes. 

• The How Sunscreens Block: The Absorption of UV Light PowerPoint focuses on the details of how 
matter absorbs light. The slides start with the more familiar concept of the emission of light by atoms 
and progress to absorption of light by atoms, then absorption of light by organic molecules, and finally 
absorption of light by inorganic compounds. The Absorption Summary Student Handout should help 
students pull make connections between a chemical's structure and its absorptive properties. 

• The Student Reading on Absorption provides more details about this key interaction between light 
and matter. 

• The Reflecting on the Guiding Questions Worksheet asks students to connect their learning from the 
activities in the lesson to the overall driving questions of the unit. 

Essential Questions (EQ) 

What essential questions will guide this unit and focus teaching and learning? 

1. What are the most important factors to consider in choosing a sunscreen? 

2. How do you know if a sunscreen has "nano" ingredients? 

3. How do "nano" sunscreen ingredients differ from most other ingredients currently used in sunscreens? 

Enduring Understandings (EU) 

Students will understand: 

(Numbers correspond to learning goals overview document) 

1. How the energies of different wavelengths of light interact differently with different kinds of matter. 

Key Knowledge and Skills (KKS) 

Students will be able to: 

(Numbers correspond to learning goals overview document) 

1. Describe the mechanisms of absorption and scattering by which light interacts with matter. 



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Table 2.27: Absorption Timeline 



Day 



Activity 



Time 



Materials 



Day 1 (50 min) 



Homework: Absorption 
of Light by Matter: Stu- 
dent Reading 
Show How Sunscreens 
Block: The Absorption 
of UV Light PowerPoint 
Slides, using the embed- 
ded question slides and 
teacher's notes to start 
class discussion. 
Discuss the readings 
and any questions stu- 
dents have about the 
PowerPoint slides. 



20 min 



35 min 



Copies of Absorption of 
Light by Matter: Stu- 
dent Reading 
How Sunscreens Block: 
The Absorption of UV 
Light PowerPoint Slides 
& Teacher Notes 
Copies of Absorption 
Summary: Student 

Handout 
Computer and projector 



Have students work in- 
dividually or in small 
groups to fill out the 
Reflecting on the Guid- 
ing Questions: Student 
Worksheet. 

Bring the class together 
to have students share 
their reflections with 
the class. 

This is also a good 
opportunity for you to 
address any miscon- 
ceptions or incorrect 
assumptions from stu- 
dents that you have 
identified in the unit up 
till now. 



5 min 



10 min 



Copies of Reflecting on 
the Guiding Questions: 
Student Worksheet 



Reflecting on the Guid- 
ing Questions: Teacher 
Instructions & Answer 
Key 



How Sunscreens Block 



261 



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The Absorption of UV Light 

Prelude: Emission of Light by Atoms 

• An e~ falls from a higher energy state to a lower one 

— A photon with the exact energy difference between the levels is released 



Single electron falling from 
energy level E1 to EO 



E, 



photon 



2.48 eV 




hu=2.48 eV 



Figure 2.45 



Each atom has characteristic energy level transitions which create an atomic spectrum 



higher energy excited states 
second excited state 

first excited state 



ground state I — * — 1 




Electronic transitions and visible emission 
spectrum for a Helium atom 

Figure 2.46 



Prelude: Absorption of Light by Atoms 

• Absorption is just the reverse 
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262 



photon 



Single electron transition 
From E to E^ 




hu=2.48 eV 



E, 



2.48 eV 



Figure 2.47 

— Only a photon with energy exactly corresponding to the energy of transition of an electron can 
be absorbed 

The different transitions produce absorption spectrums of discrete lines 



higher energy excited states 
second excited state 

first excited state 



ground state 






Electronic transitions and visible 
absorption spectrum for a Helium atom 



Figure 2.48 



Prelude: Emission versus Absorption 



Emission 

Engery released at 
specific wavelength 



Absorption 

Engery taken in from 
specific wavelength 





' 


E, photon 




T s\/\r- 


1 


\ i 


' hu=2.48 eV 



photon ■ 


k | E ' 


■AAA 


2.48 eV 
1 


hu=2.48 eV 


1 

1 E_ 



Emission spectrum only 

shows wavelength emitted 



Absorption spectrum 
shows all wavelength 
except those absorbed 




Figure 2.49 

If atomic absorption produces absorption lines, what do you think molecular absorption look 
like? 



263 



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Organic Molecules: Energy Levels 

• Molecules have multiple atoms which can vibrate and rotate in relation to each other 

— Each kind of vibration / rotation = different energy state 

• Many more energy transitions possible 



Incoming 
UV radiation 



* 






Excited 
Molecule 



. ! A* 



X 



higher energy excited states 
second excited state 

first excited state 




ground state 



Figure 2.50 



Organic Molecules: Absorption 



Many closely spaced energy transitions mean that instead of absorbing exact frequencies of light, 
molecules absorb groups of frequencies 



Atomic 
Absorption 



higher energy excited states 
second excited state 

first excited state 



ground state 



I 




W»» (length <n«( 



Figure 2.51 



Organic Molecules: Absorption Curve 



The many closely spaced absorption lines combine to make an absorption band: 

Peak absorption and absorption range vary by molecule 

— Molecules are usually strong UVB or UVA absorbers but not both 



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264 



Molecular 
Absorption 



higher energy excited states 
second excited state 

first excited state 



ground state 





W*v t length inm) 



Figure 2.52 



Absorption range 
for a new 
sunscreen 
molecule under 
testing 



New Sunscreen Absorption 




200 250 300 350 400 

Wav elength (nm) 

Figure 2.53 



Range: 255 - 345 nm 
Peak: 310 nm 



265 



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Organic Molecules: UV Protection 

• Different ingredients are good for blocking different parts of the UV spectrum 



On* Sunicrim Ingrtdient 



Two Sunccraan Ingredient* 





200 260 300 J60 400 

Wavelength (nm| 



200 260 300 360 400 

Wavelength mmi 




200 260 300 360 400 

Wavelength mmi 



Figure 2.54 

• Using more than one kind of molecule gives broader protection 

How do you think absorption by inorganic compounds might be different than absorption by 
molecules? 

Inorganic Compounds: Energy Levels 

• Inorganic ingredients exist as particle clusters 

— Very large number of atoms involved 

— Electrons' energy depends on their position in relation to all of them 

• Huge number of different energy levels possible 




excited states 




~200 nm Ti0 2 particle ground states 




Figure 2.55 
Inorganic Compounds: Absorption I 
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Conduction Band 
(excited states) 



Valence Band 
(ground states) 



Band Gap(AE) 



Figure 2.56 



267 



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• Because the energy levels are so closely spaced, we talk about them together as energy "bands" 

— Normal energy band for electrons (ground states) is called the "valence band" 

— Higher energy band (electrons are more mobile) is called the "conduction band" 

• In each band, there are many different energies that an electron can have 

— The energy spacing between the two bands is called the "energy gap" or "band gap" 

Inorganic Compounds: Absorption II 

• Electrons can "jump" from anywhere in the valence band to anywhere in the conduction band 

— Inorganic Compounds are able to absorb all light with energy equal to or greater than the band 
gap energy 



Conduction Band 
(excited states) 



Valence Band 
(ground states) 




Inorganic Compound Absorption 

FBand Gap Energy 



750 



1000 1260 1600 

Frequency (GHz) 



Figure 2.57 
Inorganic Compounds: Absorption Curve 

• This is the same as saying that all light absorbed must have a wavelength equal to or less than the 
wavelength corresponding to the band gap energy 



• Absorption curves have sharp cutoffs at this A 

— Cutoff A is characteristic of the kind of compound 

— Doesn't depend on size of the cluster 

Inorganic Compounds: UV Protection 

• Inorganic Compounds with cut off wavelengths around 400 nm [ZnO and T1O2) are able to absorb 
almost the whole UV spectrum 

— Can be the only active ingredient in a sunscreen 

— Can also be combined with other ingredients for reasons such as appearance or cost 

— True for both nano and traditional forms (not dependant on size) 



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268 



Inorganic Compound Absorption 



1.0 



■ 

u 

c 
- 

w 


V 

.a 



:. 6 



:: o 



pBjad Cl|i Entity 



k:::o -/«,:: 1600 

Frequency (GH7) 




200 260 300 360 400 

Wavelength (nm) 



Figure 2.58 



Inorganic Compound Absorption 
1.0 



0) 

o 

C 

X 

A 

L. 

o 

T 
J3 
< 




0.5 



0.0 



200 250 300 350 400 

Wav elength (nm) 

Figure 2.59 



269 



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Table 2.28: Absorption Summary 



Atoms 



Organic Molecules 



Inorganic Compounds 



Energy Levels 



title 



higher energy excited states 
second excited state 

first excited state 



ground state 
higher energy excited states 
second group of excited states 



title 



first group of excited states 



ground states 



Conduction Band 
(excited states) 



Valence Band 
(ground states) 

Absorption 
trum 




Band Gap(AE) 




Spec- 



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270 



Table 2.28: (continued) 



Atoms 



Organic Molecules Inorganic Compounds 



Atomic Absorption 




200 250 300 350 400 

Wavelength |nm) 

Molecular Absorption 
I o 




J00 250 300 350 400 
Wavelength (nm| 




200 250 300 350 400 

Wavelength (nm| 



Challenge Question: 

Can sunscreens absorb all of the UV light that shines on our skin? 

Answer: It Depends I 

• The amount of sunscreen applied influences how much of the incoming UV light is absorbed 



Answer: It Depends II 



271 



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1 


O 

o ° 

o 

o 



U.1 


° °°o° 



Thin Layer of Application 



Thick Layer of Application 



Figure 2.60 

The concentration and dispersion of the active ingredients also influences how much of the incoming 
UV light is absorbed 







C 


o c 




o o 







o. 


o rt 




■y o 

c> o 


o°° 
o o 


0° 

a 


a o 


a ' 







High Concentration 
High Dispersion 



High Dispersion 
Low Concentration 



High Concentration 
Low Dispersion 



Summary 



Figure 2.61 



Active sunscreen ingredients absorb UV light 

— Organic molecules each absorb a specific range of wavelengths determined by their energy level 
spacing 

— Inorganic compounds absorb all wavelengths less than a critical value (which corresponds to the 
band gap energy) 

Several practical factors are important to ensure that a sunscreen provides the best possible protection 
against UV light 

— High concentration of active ingredients 



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272 



— Wide dispersion of active ingredients 

— Applying an appropriate amount of sunscreen 

Teacher Notes 

Overview 

This set of slides focuses on the details of how matter absorbs light. The slides start with the more familiar 
concept of the emission of light by atoms and progress to absorption of light by atoms, then absorption of 
light by organic molecules, then absorption of light by inorganic compounds. 

Slide 1: Title Slide 

Slide 2: Prelude: Emission of Light by Atoms 

The key concept in this slide is that the energy of the photon released is always equal to an energy difference 
between energy levels. The characteristic energy of the photon is related to its frequency and wavelength, 
and if the light is in the visible spectrum, a characteristic color. 

The different energy levels relate to the position and movement of electrons with respect to the nuclei. 

Slide 3: Prelude: Absorption of Light by Atoms 

Absorption is the complementary process to emission. Instead of light being released by the atom, the 
atom captures the energy of light that shines on it. 

In order for absorption to occur, the energy of the incoming photon must be exactly equal to the energy 
of an energy transition. This is the same principle that as for emission. 

Since there are several possible electronic transitions, there are several energies of photons that can be 
absorbed. Each of these corresponds to a specific frequency of light (E = hf). Each frequency of light in 
the visible spectrum appears as a specific color to ours eyes. This produces the visible absorption spectrum 
for helium shown in the slide. 

Important Note: Even though only the visible absorption is shown here, molecules can also absorb other 
kinds of radiation. 

Common Student Question: What happens to the light energy after it is absorbed? 

Answer: Some time after light is absorbed, the electron will fall back down to a lower energy state. This 
releases the energy which is re-emitted as a photon or group of photons, often of lower energy. After this 
happens, the electron is free to absorb a new photon of light. 

Slide 4: Prelude: Emission versus Absorption 

Note that the absorption and emission spectra have lines at the same frequencies since the photons emit- 
ted and absorbed correspond to the same electronic transitions (same difference in energy levels). The 
characteristic difference in energy levels depend on the kind on atom and these spectra can be thought of 
as atomic "fingerprints." 

Slide 5: If atomic absorption produces absorption lines, what do you think molecular ab- 
sorption looks like? (Question Slide) 

Have your students brainstorm ideas about how molecules are different from atoms and how this might 
relate to the absorption of light. 

Slide 6: Organic Molecules: Energy Levels 

Energy levels relate to the position and movement of electrons and nuclei with respect to each other. Since 
molecules have more than one nuclei (because they involve more than one atom), in addition to electronic 
energy levels, they can be in different rotational and vibrational modes based on the relative motion of the 

273 www.ckl2.org 



different nuclei. This creates multiple ground and excited energy levels for each electronic state. 

Slide 7: Organic Molecules: Absorption 

Since molecules have groups of energy levels, instead of only absorbing single frequencies of light, they 
absorb a set of closely spaced frequencies (and thus wavelengths). While this creates a curve and is 
referred to as an absorption range - it is really a set of discrete energy transitions that absorb similar 
frequencies of light. 

Note that the absorption is the strongest in the middle of the range. This is because this is the wavelength 
that corresponds to the most common energy transition. 

This is a good point in the presentation to give you students the Absorption Summary: Student Handout 
to refer to. 

Slide 8: Organic Molecules: Absorption Curve 

Note that molecule does not absorb evenly over its whole absorption range. The more peaked the absorption 
curve, the more quickly absorption drops off as you move away from the peak wavelength. 

Student Check Question: What kind of UV light does the sunscreen molecule shown in the graph 
absorb? 

Answer: Mostly UVB light. The UVB range is ~ 280 - 320 nm while the UVA range is ~ 320 - 400 nm. 
The absorption range runs from 255 nm to 345 nm and thus covers more of the UVB spectrum than the 
UVA one. In addition, from the peak at 310 nm the absorbance slope toward the shorter wavelengths 
is more gradual. You can demonstrate than there is more UVB than UVA being absorbed by drawing a 
vertical line at 320 nm and looking at the area under the curve on both sides (on the left you may want to 
draw a second cutoff line at 280 nm for the end of the UVB range). Students should notice that the area 
between the 280 and 320 nm lines (UVB region) is bigger than the area to the right of the 320 nm line 
(UVA region). 

Slide 9: Organic Molecules: UV Protection 

Different molecules have different peak absorption wavelengths, different ranges of absorption and differ- 
ences in how quickly absorption drops off ("fat" curves as compared to "skinny" ones). It is important to 
realize that even within a molecule's absorption range, it does not absorb evenly and absorption at the 
ends of the range are usually low. 

This is a good opportunity to refer back to the Summary of FDA Approved Sunscreen Ingredients: Student 
Handout which lists the absorption range for each FDA approved active ingredient. 

Student Challenge Question: Which ingredients provide good UVA protection? 

Answer: Avobenzone and Ecamsule are organic molecules that absorb in the UVA range. Zinc Oxide and 
Titanium Dioxide are inorganic compounds that absorb UVA light. 

Student Challenge Question: The upper wavelength of absorption for Octocrylene and Zinc Oxide are 
both in the UVA range very similar. How can one provide little UVA protection and one provide good 
protection? 

Answer: It has to do with the shape of the absorption curves. The absorption curve for inorganic 
compounds such as Zinc Oxide looks like a cliff, they absorb strongly up to the cutoff wavelength. The 
absorption curve for organic compounds is a peak, which means they absorb very weakly at the edge of 
their absorption range. 

Slide 10: How do you think absorption by inorganic compounds might be different than 
absorption by molecules? (Question Slide) 

Have your students brainstorm ideas about how the structure of inorganic compounds is different from 
that of molecules and how this might relate to the absorption of light. 

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Slide 11: Inorganic Compounds: Energy Levels 

Energy levels relate to the position and movement of electrons and nuclei with respect to each other. 
Because of the large number of electrons and nuclei involved in the ionic clusters, there are many closely 
spaced possible energy states available in both the ground and excited states. 

Slide 12: Inorganic Compounds: Absorption I 

The difference in energy between ground states is so small that they are thought of as a continuous energy 
band. The same is true for the excited states. Within a band, very little energy is needed to change states. 

This gap in energy between the ground states and the excited states, however, is comparatively large. This 
energy difference is called the band gap. 

Slide 13: Inorganic Compounds: Absorption II 

The band gap is basically an energy threshold. Light with any energy equal to or greater than the band 
gap energy can be absorbed because it will correspond to some transition between a ground state and an 
excited state. 

The band gap energy tells us the smallest frequency of light that can be absorbed. All other transitions 
require more energy and thus will involve light with greater energy (and thus a higher frequency) 

You may want to review the relationships between Energy and frequency (E = hf) and between frequency 
and wavelength {A = c/f) with your students to help them understand the diagrams on this and the 
following slide. 

Slide 14: Inorganic Compounds: Absorption Curve 

These two graphs show the same absorption curve graphed first as a function of frequency and then as a 
function of wavelength. Remind students that frequency and wavelength are inversely related and a higher 
frequency corresponds to a smaller wavelength (c = / * A). 

Student Discussion Question: What would the graph look like if it had transmittance (instead of 
absorbance) on the y-axis? 

Answer: The graph would be inverted; it would start low and then show a steep rise. 

Slide 15: Inorganic Compounds: UV Protection 

The energy of the band gap of ZnO corresponds to light of 380 nm meaning that it can absorb all light 
that has a wavelength of 380 nm or less. This includes almost the entire UVA range (~ 320 - 400 nm) and 
does include the entire UVB (~ 280 - 320 nm) range. 

The energy of the band gap of TiO% corresponds to a wavelength of ~ 365 nm. 

The absorption properties are based on chemical structure and thus are not affected by the size of the 
inorganic cluster. Both traditional inorganic ingredients and nano inorganic ingredients have the same 
absorption curve and absorb strongly across both the UVB and UVA range. 

Slide 16: Absorption Summary 

This slide summarizes the three kinds of absorption introduced in this PowerPoint and replicates two of 
the rows of the Absorption Summary: Student Handout. The key concept to review with students is how 
the different structure of atoms, organic molecules and inorganic compounds leads to differences in energy 
level spacing which in turn leads to the difference absorption spectrum. 

Slide 17: Can sunscreens absorb all of the UV light that shines on our skin? (Question Slide) 

This slide transitions to the idea that many molecules (or inorganic clusters) are needed to protect our 
skin. Ask your students why they think applying a thin layer of sunscreen lowers its effectiveness. 

Slide 18: Answer: It Depends I 

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In order for a molecule (or inorganic cluster) to absorb UV light, the UV light must come into contact with 
it. Sunscreens are colloidal suspensions which means that the active (absorbing) ingredients are embedded 
in a (non- absorbing) lotion. 

The greater the amount of sunscreen applied, the greater the chance that UV light will come into contact 
with an active ingredient, and thus get absorbed. 

Because the light absorbing clusters are suspended in another medium, a single layer application does not 
provide total protection. Imagine a clear sheet of plastic with some black dots on it. If you shine a light 
above it, you will see a shadow of the dots because only these specific areas block the light. If you put a 
second sheet with a different pattern of dots on it on top of the first and shone a light, you would start to 
see bigger patches of shadow. If you continue to do this with more and more sheets, eventually you will 
see a rectangular shadow as the full area of the plastic is blocked. The absorbing clusters suspended in the 
sunscreen work the same way, if you apply too thin a layer, it is like only having a few sheets of plastic. 

Layer Demonstration: You may want to do an in-class demo of the concept described above by printing 
black dots onto sheets of acetate and having the class try predict how many sheets are required to get 
"total protection". The actual number will vary with the size of the dots you make, but it is generally 
many more than student expect. 

Slide 19: Answer: It Depends II 

In addition to the amount of sunscreen, there are two factors that sunscreen companies work with to make 
sunscreens as effective as possible. The first is the concentration of the active ingredients. The more active 
ingredient molecules or inorganic clusters you have, the greater the chance that light will come into contact 
with them. 

Student Challenge Question: If a higher concentration of active ingredients makes sunscreens more 
effective, why are the concentrations listed on the bottle so low? (You may want to ask students if they 
remember the concentrations they saw in the sunscreen label activity) 

Answer: Too much of any chemical can be harmful to the skin. When the FDA approves a sunscreen 
ingredient, they also give the maximum concentration that can be used. In addition, if too much of an 
ingredient is present, it can be hard to keep it dispersed. 

Dispersion is a measure of how evenly distributed the active ingredients are throughout the sunscreen. If 
they are evenly spaced, this is good dispersion and leads to effective UV absorption. If the active ingredients 
clump together, it is easier for UV light to pass through the sunscreen without getting absorbed, and thus 
cause damage to our skin. 

Slide 20: Summary 

Key take-away points from this presentation are: 



• Chemical structure determines energy level spacing, which in turn determines what wavelength(s) of 
light are absorbed. 

• Organic sunscreen ingredients exist as discrete molecules and thus are good at absorbing narrow 
ranges of UV light. 

• Inorganic sunscreen ingredients exist as ionic clusters and thus are good at absorbing the whole UV 
range (below the band gap wavelength) 

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Reflecting on the Guiding Questions: Teacher Instructions & Answer 
Key 



You may want to have your students keep these in a folder to use at the end of the unit, or collect them to 
see how your students' thinking is progressing. You can also have a group discussion about what students 
learned from the activity that helps them answer the guiding questions. 

Discussion Idea: 

For each "What I still want to know" section, have students share their ideas and discuss whether their 
questions are scientific ones or questions of another sort. Scientific questions are questions about how the 
natural world operates that can be answered through empirical experiments. Other kinds of questions 
might be ethical in nature (e.g. do friends have a responsibility to persuade friends to use sunscreen?) or 
policy questions (e.g. should the FDA endorse the most effective sunscreens?). 

Think about the activities you just completed. What did you learn that will help you answer the guiding 
questions? Jot down your notes in the spaces below. 

1. What are the most important factors to consider in choosing a sunscreen? 
What I learned in this activity: 

Possible Answers: 

Since inorganic ingredients absorb both UVA and UVB, sunscreens that include them have broadband 
protection 

Organic ingredients each absorb a specific wavelength range that can be in the UVA or UVB range. To en- 
sure broadband protection, it is important to choose a sunscreen that has a combination of ingredients that 
will absorb both kinds of light. Avobenzone and Ecamsule are the two FDA approved organic ingredients 
that absorb strongly across the UVA range. 

Regardless of the ingredients, it is important to make sure that we use enough of the sunscreen we choose 
for it to be effective. 

What I still want to know: 

2. How do you know if a sunscreen has "nano" ingredients? 
What I learned in this activity: 

Possible Answers: 

"Nano" ingredients are smaller versions of traditional inorganic ingredients. If a sunscreen contains Zinc 
Oxide or Titanium Dioxide, they may be in nanoparticle form. 

What I still want to know: 

3. How do "nano" sunscreen ingredients differ from most other ingredients currently used in sunscreens? 
What I learned in this activity: 

Possible Answers: 

"Nano" ingredients are smaller versions of traditional inorganic ingredients which exist as ionic clusters. 
They are different from most ingredients currently used in sunscreens which are organic molecules. 

While organic molecules absorb narrow bands of the UVA or UVB spectrum, all inorganic ingredients (in- 
cluding "nano" ingredients) absorb strongly in both the UVA and UVB range up to their cutoff wavelength: 
380 nm (ZnO) or 365 nm (Ti0 2 ). 

What I still want to know: 



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How Sunscreens Appear: Interactions with Visible Light 
Teacher Lesson Plan 

Contents 

• How Sunscreens Appear: Interactions with Visible Light: Teacher Lesson Plan 

• How Sunscreens Appear: Interactions with Visible Light: PowerPoint Slides and Teacher Notes 

• Ad Campaign Project (ChemSense Activity): Teacher Instructions & Grading Rubric 

• Sunscreens & Sunlight Animations: Teacher Instructions & Answer Key 

• Reflecting on the Guiding Questions: Teacher Instructions & Answer Key 

Orientation 

This lesson provides an examination of how visible light interacts with matter to produce the appearance 
of color. There are several demonstrations embedded in the PowerPoint presentation that you can do with 
your class. 

There is a choice of activities in this lesson. Both possible activities center around animations illustrating 
the interaction between visible light and sunscreen particles or skin, but one activity has students generate 
animations while the other provides them for the students to analyze. The animation creation activity is a 
more robust project that pushes students to really probe the underlying mechanism, but if time constraints 
are an issue, the pre-made animations discussion engages students in many of the same issues. 

• The Ad Campaign Project is a ChemSense Activity that puts students in the position of designing 
an animation that shows consumers how different sized particle interact with visible light. Students 
use the dedicated ChemSense Animator to aid them in this task. This project takes two days, plus 
an extra day if students have not used the program before. 

• The Sunscreens & Sunlight Animations Activity uses a pre-made flash animation (available from 
http://nanosense.org/activities/clearsunscreen/index.html) and probing questions to let 
students explore many of the design issues they would have encountered had they created their own 
animation. 

• The How Sunscreens Appear: Interactions with Visible Light PowerPoint focuses on the details of 
how matter scatters light and the phenomenon of color. 

• The Scattering of Light by Suspended Clusters: Student Reading provides more details about this 
kind of interaction between light and matter. 

• The Reflecting on the Guiding Questions Worksheet asks students to connect their learning from the 
activities in the lesson to the overall driving questions of the unit. 

Essential Questions (EQ) 

What essential questions will guide this unit and focus teaching and learning? 

1. What are the most important factors to consider in choosing a sunscreen? 

2. How do you know if a sunscreen has "nano" ingredients? 

3. How do "nano" sunscreen ingredients differ from most other ingredients currently used in sunscreens? 

Enduring Understandings (EU) 

Students will understand: 

(Numbers correspond to learning goals overview document) 

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1. How the energies of different wavelengths of light interact differently with different kinds of matter. 

2. Why particle size can affect the optical properties of a material. 

6. How to apply their scientific knowledge to be an informed consumer of chemical products. 
Key Knowledge and Skills (KKS) 

Students will be able to: 

(Numbers correspond to learning goals overview document) 

1. Describe the mechanisms of absorption and scattering by which light interacts with matter. 

2. Describe how particle size, concentration and thickness of application affect how particles in a sus- 
pension scatter light. 

3. Explain how the phenomenon of seeing things in the world is a human visual response depending on 
how light interacts with objects. 

Table 2.29: Sunscreen Appearance Timeline (with Ad Campaign Activity) 



Day 



Activity 



Time 



Materials 



Day 1 (50 min) 



Homework: Scattering 
of Light by Suspended 
Clusters: Student Read- 
ing 

Show How Sunscreens 
Appear: Interactions 
with Visible Light Pow- 
erPoint Slides, using 
the embedded question 
slides and teacher's 
notes to start class 
discussion. 

Perform Demonstra- 
tions associated with 
PowerPoint Presenta- 
tion (optional) 



20 min 



30 min 



Copies of Scattering 
of Light by Suspended 
Clusters: Student 

Reading 

How Sunscreens Ap- 
pear: Interactions with 
Visible Light Slides & 
Teacher Notes 
Computer and projector 
Optional Demonstra- 
tion Materials: Blank 
sheet of acetate, Black 
Marker, flashlights, col- 
ored gels for flashlights, 
water, milk. 



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Table 2.29: (continued) 



Day 



Activity 



Time 



Materials 



Hand out copies of the 
Ad Campaign Project 
(ChemSense Activity): 
Student Instructions 
Talk with students 
about the goal of the 
activity, the audience 
they will be preparing 
the animation for and 
the criteria they will be 
judged on. 

Have students start to 
work in teams of 2 or 
3 to create the anima- 
tions. 

Circulate throughout 
the classroom to help 
students. 



20 min 



Photocopies of Ad Cam- 
paign Project (Chem- 
Sense Activity): Stu- 
dent Instructions 
Computer with Chem- 
Sense installed for each 
student team (2-3 stu- 
dents) 



Day 2 (50 min) 



Day 3 (50 min) 



Students continue to 50 min 
work on their anima- 
tions. Towards the sec- 
ond half of the class, en- 
courage students to fin- 
ish up their animations 
and start to think about 
how they will present 
the animations to the 
class. 

Homework: Prepare for 30 min 
Presentation of Anima- 
tion to class 

Class presentation and 35 min 
discussion of animations 
using discussion ques- 
tions in Ad Campaign 
Project (ChemSense 
Activity) : Teacher 

Instructions & Grading 
Rubric. 

Have students work in- 5 min 
dividually or in small 
groups to fill out the 
Reflecting on the Guid- 
ing Questions: Student 
Worksheet. 



Copies of Reflecting on 
the Guiding Questions: 
Student Worksheet 



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280 



Table 2.29: (continued) 



Day 



Activity 



Time 



Materials 



Bring the class together 
to have students share 
their reflections with 
the class. 

This is also a good 
opportunity for you to 
address any miscon- 
ceptions or incorrect 
assumptions from stu- 
dents that you have 
identified in the unit up 
until now. 



10 min 



Reflecting on the Guid- 
ing Questions: Teacher 
Instructions & Answer 
Key 



Table 2.30: Sunscreen Appearance Timeline (with Pre-made Animation Activity) 



Day 



Act 



Time 



Materials 



Day 1 (50 min) 



Homework: Scattering 
of Light by Suspended 
Clusters: Student Read- 
ing 

Show How Sunscreens 
Appear: Interactions 
with Visible Light Pow- 
erPoint Slides, using 
the embedded question 
slides and teacher's 
notes to start class 
discussion. 

Perform Demonstra- 
tions associated with 
PowerPoint 
Presentation (optional) 



20 min 



30 min 



Scattering of Light by 
Suspended Clusters: 
Student Reading 

How Sunscreens Ap- 
pear: Interactions with 
Visible Light Power- 
Point Slides &: Teacher 
Notes 

Computer and projector 
Optional Demonstra- 
tion Materials: Blank 
sheet of acetate, Black 
Marker, flashlights, col- 
ored gels for flashlights, 
prism, pencil, beakers, 
water, milk, acrylic 
block, laser. 



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Table 2.30: (continued) 



Day 



Act 



Time 



Materials 



Hand out copies of the 
Sunscreens & Sunlight 
Animations: 
Student Instructions & 
Worksheet. 

Have students work in 
teams of 2 or 3 to view 
the animations and an- 
swer the questions on 
the worksheet. If few 
computers are available, 
use a single computer 
and projector to make it 
a whole class activity. 



20 min 



Copies Sunscreens & 
Sunlight Animations: 
Student Instructions & 
Worksheet 

Computers with for 
each student team 
or one computer and 
projector for the class 



Day 2 (30 min) 



Whole class discussion 
of what makes large par- 
ticle sunscreens appear 
white. 

Have students work in- 
dividually or in small 
groups to fill out the 
Reflecting on the Guid- 
ing Questions: Student 
Worksheet. 

Bring the class together 
to have students share 
their reflections with 
the class. 

This is also a good 
opportunity for you to 
address any miscon- 
ceptions or incorrect 
assumptions from stu- 
dents that you have 
identified in the unit up 
until now. 



15 min 



5 min 



10 min 



Copies of Reflecting on 
the Guiding Questions: 
Student Worksheet 



Reflecting on the Guid- 
ing Questions: Teacher 
Instructions & Answer 
Key 



How Sunscreens Appear: 

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282 




Interactions with Visible Light 

The Problem With Traditional Inorganic Ingredients 




Figure 2.62 

Sunscreens with traditional size ZnO and TiOi clusters appear white on skin 

— People often don't want to use them 

— They may also use them but apply less than the recommended amount 

— This reduces blocking ability and can lead to burns 



What makes sunscreens with traditional size inorganic clusters appear white? 

And... 

...what makes our skin appear "skin-colored" in the first place? 

283 



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Figure 2.63 




Figure 2.64 



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284 



Remember the Electromagnetic Spectrum? 

•* Increasing Mttrgy 



I 




^09 « a iding* 



00001 nil 01 nm 



10 nm 1000 nm 0.01cm 




§00 "IT 



300 m 



MQ -" 



*co m 



::3< 



Figure 2.65 



• Different colors of light have different wavelengths and different energies 
Reflected Light Gives an Object its Color 

• Visible light shining on an object is either absorbed or reflected 

— Only reflected wavelengths reach our eyes 

— This makes object appear a certain color 

• Color is a function of the interaction between the light and the object 

— It's not quite right to say an object is a certain color - it depends on the light too! 

What determines which colors (wavelengths) of visible light are absorbed? 
The Leaf Molecules' Energy Levels Determine Absorption 

• Only light with the right amount of energy to excite electrons is absorbed 

• Same process as seen for UV light absorption 

— Different kinds of molecules and inorganic compounds absorb different wavelengths of light 
Chlorophyll's Visible Absorption Spectrum 

• Chlorophyll is a molecule found in many plants 

— It absorbs light to excite its electrons which are then used in photosynthesis 

• It absorbs most visible light except for green light 



This is why grass (and leaves and bushes) are green 

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This leaf absorbs red and blue light 
but reflects green light 

Figure 2.66 



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Figure 2.67 



photon 



hu=2.48 eV 




2.48 eV 



Incoming 
radiation 



Molecule with excited electrons 
jumping to higher energy levels 




Figure 2.68 



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3> 

s 

> 



- 
U 

s 
- 

— 
O 
V) 



Absorbance of Visible Light 
by Chlorophyll 




380 450 550 650 750 

Wavelength of Light (nm) 



Figure 2.69 




Figure 2.70 



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288 




Figure 2.71 



289 



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So what makes our skin appear "skin-colored"? 
Pigments in our Skin Give it "Color" 

• Pigment: 

— Molecule that absorbs certain kinds of visible light and thus appears a certain color 

• Human skin color determined by melanin 

— A group of pigment molecules 

— Each kind has a unique visible absorption spectrum 

— People can also have more or less of different kinds of melanin 

What Do Melanin Molecules Do? 




Figure 2.72 

• Each kind of melanin absorbs specific wavelengths in the visible spectrum 

— Blue/green wavelengths subtracted from the light 

• Our skin appears the color of wavelengths that are left 

— Red/brown/yellow rays reflected to our eyes 

So what makes sunscreens with traditional inorganic clusters appear white? 
Inorganic Clusters Can Scatter Visible Light 



When light encounters a cluster of atoms or ions suspended in another medium, it can be sent off in 

multiple directions 

The energy from the light is redirected without a chemical interaction with the atoms 

— This is different than absorption because no energy transformation occurs 



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290 




Figure 2.73 





V._/ 

MS? 



s 



.'I 



■ 



Figure 2.74 



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Figure 2.75 



Multiple Scattering 



• After light is redirected once, it may encounter another cluster and be redirected again 

• When this happens many times, it is called multiple scattering 

Front and Back Scattering 

Light eventually goes in one of two directions: 

• Back the way it came (back scattering) 

— Back-scattered light is reflected 

• Forwards in the same general direction it was moving (front scattering) 

— Front-scattered light is transmitted 

Scattering by Traditional ZnO and TiO<i 

• Maximum scattering occurs for wavelengths twice as large as the cluster 

— Traditional ZnO and Ti02 have a diameter > 200 nm 

— Scatter light with a A near 400 nm - this includes visible light! 

Back Scattered Light Makes the Sunscreen Look White 

• The back scattered light contains all colors in the visible spectrum 

• When this light reaches our eyes, the sunscreen appears white 



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292 



Back Scatten ng 



< 1° 



o o 
o 

o 
o o 
o 




o 



o 



,° \ ° ° 



V 



Rk,r 



Front Scattering 



Figure 2.76 



Scattering for 200 nm ZnO clusters 




200 250 300 350 400 450 500 

Wav elength (nm) 

Figure 2.77 



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Figure 2.78 




Figure 2.79 



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294 



What do you think might be different about how nano sunscreen ingredients interact with 
visible light? 

Nanosized Inorganic Clusters 

• Maximum scattering occurs for wavelengths twice as large as the clusters 

— Make the clusters smaller (100 nm or less) and they won't scatter as much visible light 



I 



Scattering for 100 nm and 200 nm ZnO clusters 




200 260 300 360 400 460 600 

Wavelength (nm) 

Figure 2.80 
Nano ZnO and TiC>2 

• As the cluster size gets smaller and smaller, less and less visible light is scattered 

• This makes the sunscreen more and more transparent 

"Clear" Sunscreen 

• Light passes through the sunscreen to the skin 

— Minimal scattering 

• Melanin can absorb the blue-green wavelengths 

— Red-yellow ones are still reflected 

• The skin appears the same as it would without the sunscreen 

— Sunscreen is "clear" 

Summary 



Our skin appears "skin colored" because melanin absorbs the blue-green light from the sun 

Large inorganic sunscreen clusters scatter all visible light back towards our eyes, creating a white 

appearance 

Nano inorganic sunscreen clusters are too small to scatter visible light, so the light reaches our skin, 

the melanin can absorb the blue-green light, and our skin appears skin colored 



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Titanium Dioxide Dispersions 

hononvl Isononancate 




15 nm 55 am 90 nm 200 am 



Figure 2.81 



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Skin 



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Figure 2.82 

296 



Teacher Notes 

Overview 

This series of slides deals with the interaction of sunscreens and visible light. (This is important to 
highlight repeatedly during this lesson as students tend to get confused with the UV light interaction they 
have already studied.) The slides begin with a brief introduction to the concept of color and its relationship 
to light as an electromagnetic wave. This foundation is then used to explain why our skin has the color 
it does and how large inorganic sunscreen ingredients interact with light to produce a white appearance. 
Finally the slides discuss nanoparticles and why they appear clear. 

There are several demonstrations embedded in this slide set that you may want to prepare ahead of time. 

For further background on light and color as well as additional classroom demonstrations, you may want to 
obtain the book "Light: Stop Faking It!" available for order online at http://store.nsta. org/showltem. 
asp?product=PB169X3 . 

Slide 1: Title Slide 

Slide 2: The Problem with Traditional Inorganic Ingredients 

Student Discussion Question: Why does the amount (thickness) of sunscreen applied matter in terms 
of ability to protect our skin? 

Answer: Because the light absorbing clusters are suspended in another medium, a single layer application 
does not provide total protection. Imagine a clear sheet of plastic with some black dots on it. If you shine 
a light above it, you will see a shadow of the dots because only these specific areas block the light. If you 
put a second sheet with a different pattern of dots on it on top of the first and shone a light, you would 
start to see bigger patches of shadow. If you continue to do this with more and more sheets, eventually you 
will see a rectangular shadow as the full area of the plastic is blocked. The absorbing clusters suspended 
in the sunscreen work the same way, if you apply too thin a layer, it is like only having a few sheets of 
plastic. 

Layer Demonstration: You may want to do an in-class demo of the concept described above by printing 
black dots onto sheets of acetate and having the class try predict how many sheets are required to get 
"total protection". The actual number will vary with the size of the dots you make, but it is generally 
many more than student expect. 

Slide 3: What makes sunscreens with traditional size inorganic clusters appear white? (Ques- 
tion Slide) 

Have your students brainstorm ideas about why sunscreens with traditional inorganic clusters might appear 
white. If your students don't bring it up on their own, prompt them to consider the mechanisms by which 
light interacts with matter (Reflection, Transmission & Absorption R + T + A = 1) 

Slide 4: What makes our skin appear "skin-colored" in the first place? (Question Slide) 

Have your students brainstorm ideas about what gives skin its color. Is it is the skin matter itself? Is it 
the light from the sun? Is it the interaction between them? Ask them how they could gather evidence to 
support their view. 

Slide 5: Remember the Electromagnetic Spectrum? 

Discussion Question: Does visible light have more or less energy than UV light? How do you know? 

Answer: Less because it has longer wavelengths (smaller frequencies) and E = hf. We also know that 
visible light isn't as dangerous as UV light because it has less energy. 

Discussion Question: What kind of visible light has the most energy? What kind has the least? What 
kind falls in the middle? 

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Answer: Blue/ violet light has the most energy because it has the smallest wavelength (greatest frequency) 
of the visible spectrum (~ 400 - 500 nm). Red light has the least energy because it has the greatest 
wavelength (smallest frequency) of the visible spectrum (~ 700 - 750 nm). Yellow/Green light falls in the 
middle with a wavelength of ~ 550 - 600 nm). One way to help students to remember this is with the 
acronym often used in art classes of "Roy G. Biv" (Red Orange Yellow Green Blue Indigo Violet) that lists 
the colors in order of increasing energy. 

Slide 6: Reflected Light Gives an Object its Color 

Color Demonstration: To do this demonstration you will need to make one or more colored flashlights 
by placing a color filter in front of a flashlight. Filters are available from Educational Innovations (http: 
//www. teachersource.com/) at ~ $12 for a full set (Item FIL-100) or you may be able to borrow some 
from your school's physics teacher. A quick and inexpensive option is to use the red and blue lenses from 
an old pair of "3D" glasses. 

Demo #1: Shine a white flashlight on a green apple in a dark room - the apple appears green because 
all light (red, orange, blue) except for the green light is absorbed. Shine a red light on the apple and it 
will appear a dark grey because there is no green light to reflect and all the light is absorbed. You can 
do similar demos with any color light and oppositely colored object. This shows that when no color is 
reflected, object appear black (black is the absence of color). 

Demo#2: Shine a red flashlight on a white piece of paper in a dark room - that part of the paper will 
appear red. Add a blue flashlight and a yellow one on top of the red one. The paper should look white 
again because all three parts of spectrum are being reflected. This shows that the appearance of white is 
the combination of all colors. (Similarly, a prism can be used to separate the different parts of white light 
back into a rainbow). 

Slide 7: What determines which colors (wavelengths) of visible light are absorbed? (Question 
Slide) 

Have your students brainstorm ideas about what might determine which colors (wavelengths) of visible 
light are absorbed by different object. If your students don't bring it up on their own, prompt them to 
remember what determined the kinds of UV light each kind of sunscreen ingredient absorbs - it is the 
energy levels in the absorbing substance. 

Slide 8: The Leaf Molecules' Energy Levels Determine Absorption 

It is important to highlight the difference between what happens to the UV light and what happens to 
the visible light. Even though both may be absorbed, absorption of UV light causes skin damage while 
absorption of visible light doesn't. 

Discussion Question: Are the energy level spacings for molecules that absorb visible light greater or 
smaller than in molecules that absorb UV light? 

Answer: The specific electron transitions caused by the absorption of visible light require less energy than 
UV transitions because visible light has less energy than UV. 

Slide 9: Chlorophyll's Visible Absorption Spectrum 

Student Challenge Question: What would the reflection graph for chlorophyll look like? 

Answer: It would be the inverse of the graph shown here, very high from ~ 460 - 650 nm with a sharp 
drop off at either side. 

Biology Connection: The light energy absorbed by the chlorophyll is used in photosynthesis to make 
ATP. The absorption causes an electron to "jump" into a higher energy state which starts the electron 
transport chain. 

The electron transport chain is a series of rapid transfers between protein complexes and simple organic 
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molecules (oxidation-reduction reactions) found in the membrane systems of the chloroplast. This series 
of reactions produces energy rich molecules such as ATP. 

Slide 10: So what makes our skin appear "skin-colored"? (Question Slide) 

Have your students brainstorm ideas about what makes our skin appear "skin-colored". If they generate 
the idea that there is something in our skin that absorbs selectively in the visible spectrum, push them to 
think about whether it is the kind of these molecules or the quantity of them that accounts for different 
skin colors. 

Slide 11: Pigments in our Skin Give it "Color" 

It is not just the amount of melanin, but the kinds of melanin that determine our skin color. The amount 
and kinds of melanin in a person's skin is an inherited trait. 

Slide 12: What Do Melanin Molecules Do? 

Different melanin molecules absorb different wavelengths of light based on the differences in the spacing of 
their energy levels. If you have covered Lesson 3 with your students, you can point out that melanin is an 
organic molecule and thus absorbs a small range of frequencies, similar to these molecules. The difference 
is that the spacing between the energy levels in melanin is smaller than for organic sunscreen molecules. 
Thus it absorbs visible light, which has less energy than UV light. 

Slide 13: So what makes sunscreens with traditional inorganic clusters appear white? (Ques- 
tion Slide) 

Have your students brainstorm ideas about what makes sunscreens with traditional inorganic clusters 
appear white. 

Possible Student Misconception #1: Students make think that sunscreen clusters absorb all colors of 
visible light, but if this were true, then the sunscreen would appear black. If students come up with this 
idea, you may want to review the demos in slide 6 with them. 

Possible Student Misconception #2: Students make think that sunscreen clusters reflect all colors of 
visible light. This is true on a macro-level, but the micro-level mechanism is different because reflection 
is a phenomenon solid objects and sunscreens are colloidal suspensions, thus the "reflection" is due to 
scattering. 

Slide 14: Inorganic Clusters Can Scatter Visible Light 

Scattering is a physical process that depends on cluster size, the index of refraction of the cluster substance 
and the index of refraction of the suspension medium. No energy transformations occur during scattering 
(like they do in absorption), energy is simply redirected in multiple directions. The wavelengths (and 
energy) of light coming in and going out are always the same. 

Important Differences between Absorption & Scattering: 

Absorption is a process that involves an energy transformation. What light can be absorbed is determined 
by a chemical's energy levels, which is determined by its chemical identity and structure. The size of the 
molecule or cluster is not important. 

Scattering is a physical process that does not involve an energy transformation. What light can be scattered 
is determined primarily by the size of suspended cluster, not its identity. 

Slide 15: Multiple Scattering 

Light scattering is a common phenomenon that many of your students will have experienced (though they 
may not realize that it...). Scattering is what allows us to "see" light go past us, because the clusters 
scatter the light as it passes. For example when you are in a dusty room on a sunny day the dust scatters 
the light and you "see" the scattered light. You can show this to students by clapping blackboard erasers 
(or shaking out any other kind of dust) near a window on a sunny day. If it isn't sunny, you can do the 

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following demonstration: 

Scattering Demonstration 

Prepare two beakers: one with 100 mL of water and one with 95 mL of water and 5 mL of milk. Place 
the beakers on a dark tabletop and turn off the lights. Shine a thin flashlight or laser pointer through the 
side of the water container and have students look at the sides of the container. Then do the same for the 
beaker with the milk in it. 

For the water beaker: You shouldn't see anything since there are no clusters to scatter the light. 

For the milk and water beaker: You should be able to see the beam in the liquid since the proteins and 
other very small clusters in the milk are suspended in the water and scatter the light. To verify that light 
is scattered in all directions you can have your students try different observation points (looking down on 
the beaker, looking at the beaker from an oblique angle). 

Slide 16: Front and Back Scattering 

Multiple scattering is a phenomenon of colloids (suspended clusters). When light is scattered, at the micro 
level it goes in many directions. At the macro level, it eventually either goes back the way it came or 
forwards in the same general direction it was moving. These are known as back- and front- scattering and 
they contribute to reflection and transmission respectively. 

Note that the formula presented earlier (Reflection + Transmission + Absorption = 100%) still holds. 
Scattering simply contributes to the "reflection" and "transmission" parts of the equation. Light that has 
been absorbed cannot be scattered. 

Slide 17: Scattering by Traditional Nano ZnO and Ti0 2 

Maximum scattering occurs when the wavelength is twice as large as the cluster size. Since traditional 
inorganic sunscreen ingredients have diameter > 200 nm, they scatter light which is near 400 nm in diameter 
- this includes light in the visible spectrum. 

Slide 18: Back Scattered Light Makes the Sunscreen Look White 

The scattering of visible light by ZnO and Ti0 2 is the cause of the thick white color seen in older sunscreens. 
When the different colors of visible light are scattered up and away by the sunscreen, they reach our eyes. 
Since the combination of the visible spectrum appears white to our eyes, the sunscreen appears white. 

If you are not planning on doing the animation activities with your class, you may want to demo the anima- 
tions at this point. The animations are available at http: //nanosense . org/activities/clearsunscreen/ 
index.html and are explained in the Sunscreens & Sunlight Animations: Teacher Instructions & Answer 
Key in this lesson. 

Slide 19: What do you think might be different about how sunscreen ingredients interact 
with visible light? (Question Slide) 

Have your students brainstorm ideas about what how nano sunscreen ingredients are different from tradi- 
tional inorganic sunscreens ingredients (they are much smaller) and how this might influence the way they 
interact with visible light (their size is much smaller than half the wavelength of visible light, thus they 
are not good scatterers for this kind of light). 

Slide 20: Nanosized Inorganic Clusters 

Note that changing the cluster size simply shifts the scattering curve to a lower wavelength. While this 
may or may not change the amount of overall scattering, it reduces the amount of scattering in the visible 
range, which is what is important in determine appearance. 

Slide 21: Nano ZnO and Ti0 2 

Advanced Content: In addition to the problem of manufacturing nanoparticles of ZnO and Ti0 2 , there 

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is an additional problem in keeping the clusters dispersed since the clusters often tend to clump together. 
This creates two problems: one, when clusters clump, the absorption of UV light can be spotty; and two, 
the effective cluster size becomes larger and the clusters are more likely to scatter visible light and appear 
white. 

You may want to talk with your students about the difference between primary cluster size and the 
dispersion cluster size. The difference is that even if you produce clusters of 15 nm, very often some of 
these will clump together in the sunscreen to form effectively larger clusters (called dispersion clusters). 
This is one reason that sunscreen manufacturers are so concerned with both the medium and the procedure 
for dispersing the clusters in the sunscreen formulation. 

For example, in the graphic shown for the 15 nm clusters the dispersion cluster size is 125 nm and for the 
35 nm clusters it is 154 nm. 

Slide 22: "Clear" Sunscreen 

When visible light is not scattered by the clusters, it passes through the sunscreen and is reflected by our 
skin (blue and green rays are absorbed by pigments in the skin and the red, yellow and orange rays are 
reflected to our eyes giving skin its characteristic color). 

Student Discussion Question: Does changing the cluster size change the UV blocking ability? 

Answer: No, decreasing the cluster size will not affect its ability to block the UV rays, because absorption 
is a chemical process and determined by the energy levels of the matter (which do not change dramatically 
with size). Thus the nano-sized clusters are still good UV blockers. 

Student Challenge Question: Why was the scattering issue never a problem for organic ingredients? 

Answer: Organic sunscreen molecules are smaller than 10 nm (usually 1-20 Angstroms) and thus do not 
scatter in the visible range. 

Slide 23: Summary 



Key take-away points from this presentation are: 



• Appearance is determined by interactions with visible light 

• Selective absorption of blue and green wavelengths by pigment molecules gives our skin its charac- 
teristic color 

• Suspended clusters ~ 200 nm in size (like traditional ZnO and 7702 sunscreen ingredients) scatter 
visible light strongly. (Maximal scattering occurs as A = 2* diameter). Scattering causes all colors of 
visible light to be reflected (back scattered) to our eyes. The combination of all colors of visible light 
appears white, hence the sunscreen appears white. 

• Suspended clusters < 100 nm in size (like nano ZnO and TiOi sunscreen ingredients) are too small 
to scatter visible light. The light passes through the sunscreen to the skin, where the blue and green 
wavelengths are absorbed, as when no sunscreen is present. The skin appears "skin colored", which 
is the same as saying that the sunscreen is clear. 

Ad Campaign Project: Teacher Instructions &; Grading Rubric 

Overview 

In this activity your students will create animations that show how UV and visible light interact with 
"large" and nano-sized zinc oxide particles. The process of making the many design decisions needed to 
create the animations will stimulate your students to consider the absorption and scattering processes in 
depth. Having them work in groups will enhance the activity since they will need to discuss and reconcile 
their different conceptions of the process. Even if your students have seen scattering animations before, 

301 www.ckl2.org 



the process of making one will give them the opportunity to integrate and solidify their understanding of 
the process. 

Important: It is very important to review student animations with the whole class at the end of the 
project so that any parts of the animations that represent the phenomenon incorrectly can be identified 
and student misconceptions can be corrected. Student will also get to see how the same phenomenon can 
be represented in multiple ways. 

Note: Your students should not have access to an existing scattering animation while they create their 
own, since this will cause them to replicate existing features without making their own design decisions. 

Sunsol, the prominent sunscreen maker, has just decided to launch a new product into the market. The 
sunscreen will use a zinc oxide (ZnO) nanopowder as its only active ingredient, and will be formulated to 
go on clear and non-greasy. Sunsol is very excited about its new product, and wants to launch a full ad 
campaign to promote it to consumers who may not be familiar with the idea of a clear sunscreen that 
offers full spectrum protection. 

Sunsol feels that it is very important for their potential customers to understand both how ZnO interacts 
with light to protect people's skin and how the size of the particles affects the sunscreen's appearance. For 
this reason, they have decided that the ad campaign should center on an animated commercial that shows 
how traditional ZnO and ZnO nanopowders interact with UV and visible light. 

Sunsol has invited several creative teams — including yours — to use the ChemSense Animator to create 
animations showing how the different sized ZnO particles suspended in the sunscreen will scatter visible 
light differently. 

The Request 

Sunsol is requesting a total of 4 animations: 

1. Sunscreen with ~ 50 nm ZnO particles interacting with UV light. 

2. Sunscreen with ~ 50 nm ZnO particles interacting with visible light. 

3. Sunscreen with ~ 300 nm ZnO particles interacting with UV light. 

4. Sunscreen with ~ 300 nm ZnO particles interacting with visible light. 

Your teacher will put you in teams and let you know which of the animations you should work on. 
Note: Groups of 2-3 students work well for this assignment. 

Table 2.31: Animation Matrix 

UV light Visible Light 

50 nm ZnO particles 1 2 

300 nm ZnO particles 3 4 

Note: The animations differ in difficulty as follows: 

1. Easy (All UV light is absorbed) 

2. Difficult (No visible light is scattered; skin absorbs blue/green light, skin appears skin colored) 

3. Easy (All UV light is absorbed) 

4. Medium (All visible light is scattered, skin appears white) 

If time allows, you may want to assign groups to work on both the UV and visible animations for a given 
size particle (e.g. Animations 1 & 2 or 3 &; 4) 

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Requirements 

Discuss the requirements and student version of the rubric together. 
All animations should contain the following elements: 

• A light source (the sun) 

• A skin surface with sunscreen lotion applied 

• ZnO particles of the required size suspended in the lotion 

• A minimum of 10 frames 

The UV light animations should also include: 

• At least 2 UVA and 2 UVB light rays interacting with the ZnO particles (and skin when appropriate) 

• All relevant blocking mechanisms for the ZnO particles in the sunscreen 

The visible light animations should also include: 

• At least 5 visible light rays interacting with the ZnO particles (and skin when appropriate) 

• A human observer and an indication of what the they see 

Things to consider in your animation 

• How thick will the sunscreen be applied? 

• What concentration of particles will the sunscreen have? 

• How will you show the different blocking mechanisms? 

• How will you indicate what the human observer sees? 

Evaluation 

Sunsol will evaluate the animations based on the following criteria: 

• All required elements are present and accurately depicted 

• Animations show correct interaction of light rays with ZnO particles (and skin) 

• All relevant blocking mechanisms shown (UV light only) 

• Animations clearly indicate what the observer sees and why (Visible light only) 

• All team member contributed and worked together to produce the animations 

Discussion 

Important: Your student's animations are models of the scattering phenomenon. In creating them, your 
students will have made tradeoffs between realism, simplicity, precision and generality. It is important to 
have your students share their animations and discuss the advantages and limitations of each model (as 
well as aspects that are inaccurately depicted) so that they do not develop misconceptions about scattering. 

Questions to answer about each model: 

• How does this model show absorption / scattering? 

• How does this model show what the observer sees? 

• What are its strengths? (What aspects of scattering does it show particularly well?) 

• What are its limitations? (What aspects of scattering are not shown well?) 

303 www.ckl2.org 



• Is there anything that seems inaccurately depicted? 

• What could be done (within the structure of the animation) to address some of these limitations? 

Questions to answer about the group of models as a whole: 

• What do the different animations have in common? How do they show things in similar ways? 

• What things do the animations show in different ways? Are different animations better at showing 
different aspects of the phenomenon? 

• If different models can be used to represent a phenomenon, how do we know which one is "better"? 
(Models which best align with or represent the empirical data we have are better.) 

Table 2.32: Rubric for Ad Campaign Evaluation — UV Light Animations 



Category 



Novice (1) Ab- Apprentice (2) Skilled (3) Ade- Masterful (4) 

sent, missing or Partially devel- quately developed Fully developed 
confused oped 



Required Ele- 
ments 

• Light source 

• Skin surface 


- 2 of the re- 
quired elements 
are present. 


3 - 4 of the re- 
quired elements 
are present. 


5 - 6 of the re- 
quired elements 
are present. 


All 7 required ele- 
ments are present. 


• Sunscreen 
lotion 

• Suspended 
ZnO parti- 
cles 

. 2+ UVA 










rays 

• 2+ 


UVB 










rays 
. 10 + 


frames 














Few of the re- 
quired elements 
are accurately 
depicted. 


Some of the re- 
quired elements 
are accurately 
depicted. 


Most of the re- 
quired elements 
are accurately 
depicted. 


All of the required 
elements are accu- 
rately depicted. 



Interactions of 

light rays with 
ZnO particles (and 
skin when appro- 
priate) correctly 
shown 



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304 



Table 2.32: (continued) 



Category 



50 nm: 



. All light 

is only 

absorbed 

. UVA / UVB 
interact the 
same 

300 nm: 

• Light is 
both ab- 
sorbed and 
scattered 

. UVA / UVB 
interact the 
same 

All relevant block- 
ing mechanisms 
correctly shown 
50 and 300 nm: 

• Absorption 
shows light 
energy being 
captured 

by ZnO 

particles 

300 nm only: 

• Scattering 
shows light 
being redi- 
rected in 
multiple 
directions 



Novice (1) Ab- Apprentice (2) Skilled (3) Ade- Masterful (4) 

sent, missing or Partially devel- quately developed Fully developed 
confused oped 



Few or no key as- 
pects of the in- 
teraction are cor- 
rectly shown. 



Some aspects of 
the interaction are 
correctly shown. 



Most key aspects 
of the interac- 
tion are correctly 
shown. 



All key aspects of 
the interaction are 
correctly shown. 



Few or no key as- 
pects of the block- 
ing mechanism are 
correctly shown. 



Some key aspects 
of the blocking 
mechanism are 
correctly shown. 



Most key aspects 
of the blocking 
mechanism are 
correctly shown. 



All key aspects 
of the blocking 
mechanism are 
correctly shown. 



305 



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Table 2.32: (continued) 



Category 



Novice (1) Ab- Apprentice (2) Skilled (3) Ade- Masterful (4) 

sent, missing or Partially devel- quately developed Fully developed 
confused oped 



Teamwork 




Few team mem- 


Some team mem- 


Most team mem- 


All team members 






bers contributed 


bers contributed 


bers contributed 


contributed to the 


• All team 
members 


to the project. 


to the project. 


to the project. 


project. 


contributed 










significantly 










to 


the 










project 












• Group 












worked 


to- 










get her 


to 










manage 












problems 


as 










a team 
















Group did not ad- 


Group did not 


Problems in the 


Group worked 






dress the problems 


manage problems 


group managed by 


together to solve 






encountered. 


effectively. 


one or two individ- 
uals. 


problems. 


Table 2.33: 


Rubric for Ad Campaign Evaluation 


i — Visible Light Animations 


Category 




Novice (1) Ab- 


Apprentice (2) 


Skilled (3) Ade- 


Masterful (4) 






sent, missing or 


Partially devel- 


quately developed 


Fully developed 






confused 


oped 







Required Ele- 


- 2 of the re- 


3 - 4 of the re- 


5 - 6 of the re- 


All 7 required ele- 


ments 


quired elements 


quired elements 


quired elements 


ments are present. 




are present. 


are present. 


are present. 




• Light source 










• Human 










observer 










• Skin surface 










• Sunscreen 










lotion 










• Suspended 










ZnO parti- 










cles 










• 5+ visible 










light rays 










• 10 + frames 












Few of the re- 


Some of the re- 


Most of the re- 


All of the required 




quired elements 


quired elements 


quired elements 


elements are accu- 




are accurately 


are accurately 


are accurately 


rately depicted. 




depicted. 


depicted. 


depicted. 




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306 







Table 2.33: (continued) 



Category Novice (1) Ab- Apprentice (2) Skilled (3) Ade- Masterful (4) 

sent, missing or Partially devel- quately developed Fully developed 
confused oped 

Interactions of 

light rays with 
ZnO particles (and 
skin when appro- 



priate) 
shown 
50 nm: 



correctly 



No scatter- 
ing 

Blue /green 
light ab- 

sorbed by 
skin 

Few or no 
key aspects 
of the ob- 
server's view 
are correctly 
shown. 



Few or no key as- 
pects of the in- 
teraction are cor- 
rectly shown. 



Some aspects of 
the interaction are 
correctly shown. 



Most key aspects 
of the interac- 
tion are correctly 
shown. 



All key aspects of 
the interaction are 
correctly shown. 



What the observer 
sees and why they 
see is correctly 
shown 
50 nm: 

• Skin 

Peach/Brown 
color 



Few or no key as- 
pects of the ob- 
server's view are 
correctly shown. 



Some key aspects 
of the observer's 
view are correctly 
shown. 



Most key aspects 
of the observer's 
view are correctly 
shown. 



All key aspects 
of the observer's 
view are correctly 
shown. 



300 nm: 



Sunscreen 
White color 



307 



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Table 2.33: (continued) 



Category 



Novice (1) Ab- Apprentice (2) Skilled (3) Ade- Masterful (4) 

sent, missing or Partially devel- quately developed Fully developed 
confused oped 



Teamwork 




Few team mem- 


Some team mem- 


Most team mem- 


All team members 






bers contributed 


bers contributed 


bers contributed 


contributed to the 


• All team 
members 


to the project. 


to the project. 


to the project. 


project. 


contributed 










significantly 










to 


the 










project 












• Group 












worked 


to- 










get her 


to 










manage 












problems 


as 










a team 
















Group did not ad- 


Group did not 


Problems in the 


Group worked 






dress the problems 


manage problems 


group managed by 


together to solve 






encountered. 


effectively. 


one or two individ- 
uals. 


problems. 



Sunscreens & Sunlight Animations: Teacher Instructions & Answer Key 

This animation worksheet is best used as an in class activity with small groups in order to give students 
a chance to discuss the different things they notice in the animations. If you have a limited amount of 
in-class time you may want to do it as a whole class activity or assign it for homework (if all your students 
have access to the internet) with a follow-up class discussion. 

Important: These models are meant to provoke questions and start a discussion about how the scattering 
mechanism works as well as about the process of making decisions about how to represent things in models. 
They are not perfect and are not meant to be shown to students simply as an example of "what happens". 

Introduction 

There are many factors that people take into account when choosing which sunscreen to use and how much 
to apply. Two of the most important factors that people consider are the ability to block UV and the 
visual appearance of the sunscreen (due to the interaction with visible light). You are about to see three 
animations that are models of what happens when sunlight (both UV and visible rays) shine on: 

• Skin without any sunscreen 

• Skin protected by 200 nm ZnO particle sunscreen 

• Skin protected by 30 nm ZnO particle sunscreen 

Open the animation file as instructed by your teacher and explore the animations for different sunscreen 
and light ray options. Then choose the sunscreen option and wavelength(s) of light as indicated to answer 
the following questions. 



Viewing the Animations Online: 

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308 



To view the animations, have your students navigate to the Clear Sunscreen Animation web page at 
http://nanosense.org/activities/clearsunscreen/sunscreenanimation.html 

Downloading the Animations: 

If you have a slow Internet connection or want to have a copy of the animation on your computers for 
offline viewing, go to the Clear Sunscreen Materials web page at http://nanosense.org/activities/ 
clearsunscreen/ and download the files "sunscreenanimation.html" and "sunscreenanimation.swf" to the 
same folder. To view the animation, simply open the file "sunscreenanimation.html" in your web browser. 

Questions 

Questions 1-2 look at the effects of the UV rays. 

Questions 3-7 look at the effects of the visible rays. 

Questions 8-9 ask "what if" questions about changing the animation. 

Question 10 asks students to consider the tradeoffs, strengths and limitations of the animations as a model 
of the interaction of light and sunscreens. 

1. Select the UVA and UVB wavelengths of light with no sunscreen and click the play button. 

a. What happens to the skin when the UV light reaches it? 
The skin is damaged. 

b. How is the damage caused by the UVA rays different from the damage caused by the UVB rays? (You 
may want to play the animation with just UVA or UVB selected to answer this question) 

In the animation UVB light causes a burn on the skin's surface and UVA light causes the breakdown in 
skin fibers deeper in the skin that cause premature aging. 

c. Based on what you know about the different energies of UVA and UVB light why do you think this 
might happen? 

The UVB light causes more immediate damage to the first cells it encounters because it is high energy. 
The UVA light is lower in energy and can penetrate deeper into the skin before it does damage. 

Both UVB and UVA light also can lead to DNA mutations that cause cancer which is not shown in the 
animation. 

2. Now leave UVA and UVB light selected and try playing the animation first with the 30 nm ZnO 
sunscreen and then with the 200 nm ZnO sunscreen. 

a. What kind of sunscreen ingredients are shown in each animations? 
The 30 nm ZnO is a nanosized inorganic ingredient. 

The 200 nm ZnO sunscreen is a traditional inorganic ingredient. 

b. What happens to the UV light in the animation of 30 nm ZnO particle sunscreen? 
The UV light is completely blocked via absorption. 

c. What happens to the UV light in the animation of 200 nm ZnO particle sunscreen? 
The UV light is completely blocked via absorption. 

d. Is there any difference in how the UV light interacts with the 30 nm ZnO particles versus the 200 nm ZnO 
particles? Explain why this is so based on your understanding of how the sunscreens work to block UV 
light. 

There is no difference in how the 30 nm and 200 nm ZnO particles interact with the UV light. This is 
because absorption depends on the energy levels in the substance which are primarily determined by the 
substance's chemical identity, not the size of the particle. 

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e. Is there any difference in how the two kinds of UV light interact with the sunscreens? Explain why this 
is so based on your understanding of how the sunscreens work to block UV light 

Both UVA and UVB light are fully absorbed because ZnO absorbs strongly for all wavelengths less than 
~ 380 nm. 

Students may point out that wavelengths of 380 - 400 nm are UVA light that might not be absorbed. This 
is true and can be discussed at part of the final questions which address the limitations of using models. 

3. Select the visible light option and play the animation for each of the sunscreen conditions. What 
happens to the visible light in each animation and what does the observer see? 

a. Skin without any sunscreen 

The photons of light pass through the air to the skin. At the skin's surface, most of the blue-green 
(~ 400 - 550 nm) wavelengths of light are absorbed by pigments in the skin, while the red-orange-yellow 
(~ 550 - 700 nm) wavelengths of light are reflected and reach the observer's eye. The observer sees the 
surface of the skin. (Different skin colors are caused by different amounts and types of the skin pigment 
melanin.) 

b. Skin with 200 nm Zno particles sunscreen 

The photons of light pass through the air and are refracted (bent) as they enter the sunscreen. They are 
then scattered by the ZnO particles multiple times until they emerge from the sunscreen and are again 
refracted (bent). Since large particles of ZnO scatter all wavelengths of light equally, all of the different 
photon wavelengths reach the observer who sees an opaque white surface. (Note that even though the 
animation shows the different colored photons reaching the observer at different times, in reality there are 
many photons of each color reaching the observer at the same time.) 

c. Skin with 30 nm ZnO particle sunscreen 

The photons of light pass through the air and are refracted (bent) as they enter the sunscreen. They 
pass through ZnO particles without being scattered and at the skin's surface, most of the blue-green 
(~ 400 - 550 nm) wavelengths of light are absorbed by pigments in the skin, while the red-orange-yellow 
(~ 550 - 700 nm) wavelengths of light are reflected. They then pass through the sunscreen again and are 
refracted (bent) when they pass to the air before they reach the observer's eye. The observer sees the 
surface of the skin and we say that the sunscreen is "clear". 

4. What determines what the observer sees? (Do they see the skin or the sunscreen? What color do they 
see?) 

You see whatever substance the light touched last before it reaches your eye. 

The color is determined by which wavelengths of light are absorbed and which are reflected or scattered. 

5. How does scattering affect what the observer sees? 

In the no sunscreen and the 30 nm ZnO animations the light doesn't scatter. Without scattering, the 
light that reaches the observer's eyes is the light reflected by the skin (which passes through the sunscreen 
without being changed) so this is what they see. Since the pigments in the skin absorb blue- green light, 
skin generally has a reddish color. 

When the light scatters (in the 200 nm ZnO animation), the light reaching the observers eyes is reflected 
off of the ZnO particles so this is what they see. Since the ZnO scatters (and thus reflects) all wavelengths 
of light equally, it appears white. 

6. What variables don't change between the two animations with sunscreens? 

The sunscreen solvent, the thickness of the sunscreen layer, the wavelengths of the photons, the identity 
of the sunscreen's active ingredient, the approximate concentration of the ZnO particles (by weight) 

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7. What variable determines if the visible light scatters or not? 

The size of the ZnO particles compared to the wavelength of light. Maximum scattering occurs when the 
particle diameter is one half the wavelength of light (~ 300 nm for visible light). For particles much smaller 
than this (e.g. 50 nm), there is very little scattering. 

8. What would happen if we applied the large particle sunscreen in a layer only half as thick as the one 
shown? How would this affect its appearance? How would it affect its UV blocking ability? 

Appearance: There will be less ZnO particles to scatter the light and so some of the photons will reach 
the skin layer. The sunscreen would not appear fully white but semitransparent (you would see the skin 
but it would have a whitish color). 

Blocking Ability: Because there are less ZnO particles, the sunscreen won't be as effective at blocking 
UV. 

9. What would happen if the observer (eye) moved 3 steps to the left to look at the skin? 

Only 5 photons are shown in each animation, but in reality there are many more photons involved both 
entering and leaving the sunscreen at different angles. Thus there are many photons that never reach the 
eye of the specific observer shown in the animations. If the observer moves to a new position, they will 
have different photons reach their eye, but the appearance of the skin / sunscreen remains the same. 

10. When we make a model (such as these animations) we make tradeoffs between depicting the phe- 
nomenon as accurately as possible and simplifying it to show the key principles involved. 

a. Are the different elements of the animation drawn on the same size scale? If not, which ones aren't? 
How do these affect the animation's ability to depict the scattering mechanism? Which elements in the 
animation are really on or close to the nanoscale? Which are on the macroscale? Which are on the cosmic 
scale? 

To Scale: Wavelength of light and ZnO particle size (this is a key relationship) 

Not to Scale: Eye of observer (this is done to show what is seen, but important to note that there are 
many more photons than shown in the animation and most of them don't reach the observer's eye) 

Nanoscale: ZnO particles, photons 

Macroscale: Skin, sunscreen lotion, observer 

Cosmic Scale: Sun 

b. What are some other ways these animations have simplified the model of the real world situation they 
describe? 

Example Simplifications: 

• The UVA and UVB light is shown as two identical photons when in reality there are many more 
photons involved. 

• The wavelength of the two photons of UVA and UVB light is shown to be the same when in reality 
each of these kinds of lights represents a range of wavelengths. 

• The ZnO particles are shown as "solid" balls when in reality they are clusters of ions. 

• All of the ZnO particles are shown to be the same size, but whenever the particles are produced in 
reality there is a distribution of particles sizes. 

• The damage of the UV rays to the skin doesn't shown the DNA mutations which lead to cancer 
because of the size and time scale involved. 

• The sunscreen solvent is a pale yellow, but it should be clear since it does not scatter (or absorb) 
light. How else could this be shown in the animations? 

c. What are some of the benefits of making a simplified model? What are some of the drawbacks? 

311 www.ckl2.org 



Benefits: Easier to see the core of what is going on for particular aspects of the phenomenon; can highlight 
one particular aspect you want to focus on. 

Drawbacks: Viewers won't realize what details are missing and may develop misconceptions about the 
phenomenon; viewers may also not realize the true complexity of the phenomenon and think that it is 
simpler than it actually is. There is a tradeoff between realism, precision and generality. 

Reflecting on the Guiding Questions: Teacher Instructions & Answer 
Key 

You may want to have your students keep these in a folder to use at the end of the unit, or collect them to 
see how your students' thinking is progressing. You can also have a group discussion about what students 
learned from the activity that helps them answer the guiding questions. 

Discussion Idea: 

For each "What I still want to know" section, have students share their ideas and discuss whether their 
questions are scientific ones or questions of another sort. Scientific questions are questions about how the 
natural world operates that can be answered through empirical experiments. Other kinds of questions 
might be ethical in nature (e.g. do friends have a responsibility to persuade friends to use sunscreen?) or 
policy questions (e.g. should the FDA endorse the most effective sunscreens?). 

Think about the activities you just completed. What did you learn that will help you answer the guiding 
questions? Jot down your notes in the spaces below. 

1. What are the most important factors to consider in choosing a sunscreen? 
What I learned in this activity: 

Possible Answers: 

It is also important to choose a sunscreen that we like in terms of appearance to make sure that we use 
enough of it to be effective. 

What I still want to know: 

2. How do you know if a sunscreen has "nano" ingredients? 
What I learned in this activity: 

Possible Answers: 

"Nano" ingredients are smaller versions of traditional inorganic ingredients {ZnO and Z702)- 

Traditional ZnO and T1O2 clusters are > 200 nm in diameter. When clusters are suspended in another 
medium (like active sunscreen ingredients in the sunscreen lotion) they can scatter light. Light is maximally 
scattered when its wavelength is twice the diameter of the cluster, so these clusters scatter significantly in 
the visible range. Some of the scattered light is back-scattered (reflected) back towards our eyes. Since 
this light is of all visible colors, it combines to appear white. 

ZnO and TiO<i nanoparticles are much small in size with clusters of < 100 nm in diameter. Because of their 
size, they do not scatter appreciably in the visible range. Since visible light is not scattered by the clusters, 
it passes through the sunscreen and is reflected by our skin (blue and green rays are absorbed by pigments 
in the skin and the red, yellow and orange rays are reflected to our eyes) giving skin its characteristic color, 
thus the sunscreen appear clear. 

If a sunscreen contains Zinc Oxide or Titanium Dioxide, but appears clear on our skin, then it likely 
contains nanoparticles of ZnO or 7702- 

What I still want to know: 

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3. How do "nano" sunscreen ingredients differ from most other ingredients currently used in sunscreens? 

What I learned in this activity: 

Possible Answers: 

Most ingredients currently used in sunscreens are organic ingredients. These are individual molecules that 
absorb narrow bands of the UVA or UVB spectrum. 

"Nano" sunscreen ingredients are inorganic and very similar to traditional inorganic ingredients (large ZnO 
and TiC>2 clusters); however they appear clear on our skin. 

Nano clusters are made up of the same kinds of atoms and have the same formula unit and the larger 
inorganic clusters, thus they absorb the same kinds of UV light: all wavelengths less than 380 nm [ZnO) 
or 365 nm (7702). 

However, because the nano inorganic clusters are much smaller in size than traditional inorganic ones 
(< 100 nm in diameter as opposed to > 200 nm), they don't scatter visible light (maximum scattering 
occurs at A = 2 * diameter) and thus appear clear on our skin. 

What I still want to know: 

Culminating Activities 
Teacher Lesson Plan 

Contents 

• Culminating Activities: Teacher Lesson Plan 

• Consumer Choice Project: Teacher Instructions & Grading Rubric 

• The Science Behind the Sunscreen Quiz: Teacher Answer Key 

• Clear Sunscreen Final Reflections: Teacher Instructions & Answer Key 

Orientation 

This lesson is designed to have students consolidate their learning and reflect on how their ideas have 
changed over the course of the unit. 

• The Consumer Choice Project is a performance assessment that has students integrate their learning 
from the unit into a pamphlet to inform consumers about nanoparticulate sunscreens, how they work 
and their benefits and drawbacks. It includes a teacher grading rubric and peer feedback forms. 

• The Science Behind the Sunscreen Quiz is a traditional assessment that asks students a series of 
closed and open ended questions about the material in the unit. 

• The Final Reflections activity asks students to review their reflections from each of the unit activities, 
answer the essential questions of the unit and compare their current thinking with their thinking from 
the beginning of the unit. Students also are asked to identify how their ideas have changed and what 
things (if any) they are still unsure about. These can serve as final discussion points or ideas for 
future investigation. 

Essential Questions (EQ) 

What essential questions will guide this unit and focus teaching and learning? 

1. What are the most important factors to consider in choosing a sunscreen? 

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2. How do you know if a sunscreen has "nano" ingredients? 

3. How do "nano" sunscreen ingredients differ from most other ingredients currently used in sunscreens? 

Enduring Understandings (EU) 

Students will understand: 

(Numbers correspond to learning goals overview document) 

1. How the energies of different wavelengths of light interact differently with different kinds of matter. 

2. Why particle size can affect the optical properties of a material. 

3. That there may be health issues for nanosized particles that are undetermined at this time. 

4. That it is possible to engineer useful materials with an incomplete understanding of their properties. 
6. How to apply their scientific knowledge to be an informed consumer of chemical products. 

Key Knowledge and Skills (KKS) 

Students will be able to: 

(Numbers correspond to learning goals overview document) 

1. Describe the mechanisms of absorption and scattering by which light interacts with matter. 

2. Describe how particle size, concentration and thickness of application affect how particles in a sus- 
pension scatter light. 

3. Explain how the phenomenon of seeing things in the world is a human visual response depending on 
how light interacts with objects. 

4. Evaluate the relative advantages (strong blockers, UVA protection) and disadvantages (possible car- 
cinogenic effects, not fully researched) of using nanoparticulate sunscreens. 

Table 2.34: Culminating Activities Timeline (Pamphlet Performance Assessment) 



Day 



Activity 



Time 



Materials 



Day 1 (50 min) 



Hand out the Consumer 10 min 
Choice Project: Stu- 
dent Instructions and 
walk through the as- 
signment and grading 
criteria with students. 
Assign or let students 
pick the groups or 3 or 
4 that they will work in. 

Have students work in 40 min 
their teams to create the 
pamphlets. 

Circulate through the 
room answering ques- 
tions and probing stu- 
dent work. 



Copies of Consumer 
Choice Project: Stu- 
dent Instructions 



White paper and col- 
ored markers or com- 
puters with access to a 
printer. 



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314 



Table 2.34: (continued) 



Day 



Activity 



Time 



Materials 



Day 2 (50 min) 



Homework: Continue to 30 min 
work on the pamphlets 

• Note: Depending 
on the depth of 
student work you 
may want to ex- 
tend the activity 
to a second class 
period. 

Have students share 25 min 
their pamphlets with 
the whole class and fill 
out the peer feedback 
forms for other teams' 
pamphlets. 

Have students work in- 10 min 
dividually or in small 
groups to fill out the 
Reflecting on the Guid- 
ing Questions: Student 
Worksheet. 

Discuss the Essential 15 min 
Questions and the 
group's collective abil- 
ity to answer them 
based on the work done 
in the unit and answer 
any remaining student 
questions. 



Copies of Consumer 
Choice Project: Peer 
Feedback Form 



Copies of Final Reflec- 
tions: Student Work- 
sheet 



Copies of Final Reflec- 
tions: Teacher Instruc- 
tion & Answer Key 



Table 2.35: Culminating Activities Timeline (Quiz) 



Day 



Activity 



Time 



Materials 



Day 1 (50 min) 



Hand out the quiz and 
have students work on it 
on their own. 
Have students work in- 
dividually or in small 
groups to fill out the 
Reflecting on the Guid- 
ing Questions: Student 
Worksheet. 



25 min 



10 min 



Copies of The Science 
Behind the Sunscreen: 
Student Quiz 
Copies of Final Reflec- 
tions: Student Work- 
sheet 



315 



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Table 2.35: (continued) 



Day 



Activity 



Time 



Materials 



Day 2 (15 min) 



Discuss the Essential 15 min 
Questions and the 
group's collective abil- 
ity to answer them 
based on the work done 
in the unit and answer 
any remaining student 
questions. 

Hand back the corrected 15 min 
quizzes and go over the 
answers with students. 



Copies of Final Reflec- 
tions: Teacher Instruc- 
tion & Answer Key 



The Science Behind 
the Sunscreen Quiz: 
Teacher Answer Key 



Consumer Choice Project: Teacher Instructions &; Grading Rubric 

Introduction 

SmartShopper, the consumer advocacy group, has heard a lot in the media about the new clear sunscreens 
with nanoparticulate ingredients coming out on the market. Consumers have been contacting them lately 
to ask them if these new products are better than traditional sunscreens, if they are safe to use, and how 
to know if a sunscreen uses nanoparticulate ingredients. To help consumers decide whether these products 
are right for them, SmartShopper has decided to produce a pamphlet that tells consumers all they need to 
know about these new products. SmartShopper also will need to take a position on whether or not they 
endorse the use of the sunscreens and justify this position based on a comparison of the benefits and risks 
backed up with science. They turn to you and your team to create this pamphlet. 

Requirements 

SmartShopper asks that your pamphlet makes full use of both sides of an 8.5 x 11 piece of paper folded 
into thirds for easy distribution (see "How to Make a Pamphlet") and contains: 

• A brief overview of what nanoparticulate sunscreen ingredients are and how they are similar and how 
they are different from other active sunscreen ingredients. 

Nanoparticulate sunscreen ingredients are inorganic UV blockers. This means that they are made out of 
the same atoms and have an ion lattice structure like standard inorganic sunscreen ingredients, but the 
particle size (the number of atoms that group together) is much smaller. 

They are different from organic UV blockers which are usually conjugated carbon compounds and exist as 
discrete molecules (i.e. particle size doesn't vary). 

• A list of common nanoparticulate active sunscreen ingredients and how to know if your sunscreen 
contains them. 

Zinc Oxide and Titanium Dioxide 

The sunscreen may claim "goes on clear" if the nano-versions are used. You can also look at the actual 
color of applied sunscreen to see if it is the nano- version. 



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316 



• An explanation of how sunscreens with nanoparticulate ingredients work to block UV light from 
reaching the skin and the benefits of using them (including advantages over other sunscreen ingredi- 
ents). 

Sunscreens with nanoparticulate ingredients block UV rays by absorbing them. Benefits are full UV 
coverage, clear appearance and no allergic reactions (traditional inorganic ingredients give full coverage 
but are not clear (often causing people to use too little); organic ingredients are clear but only block part 
the UV range and can cause allergic reactions) 

• A explanation of why nanoparticulate sunscreen ingredients are clear and a diagram that illustrates 
the science principles involved. 

The opacity of a material depends on the degree to which it scatters light. 

Nanoparticles are so much smaller than the wavelength of visible light that they do not scatter it effectively. 

Thus, visible light passes through the sunscreen, to the skin's surface where some rays (blue / green) 
are absorbed and some rays (red / yellow) are reflected. When the receptors in our eyes received by the 
reflected rays we they produce the image of our skin that we see. 



A transmission versus wavelength graph that supports this explanation. 



Students do not need to create this graph themselves - they can use a graph from the unit materials or find 
one online. The important concept is that they interpret the graph correctly by relating the % transmission 
at different wavelengths with appearance (white/clear) and UV blocking ability for differently size ZnO 
particles. 

• An explanation of the possible downsides / dangers of using sunscreens with nanoparticulate ingre- 
dients. 

The process of absorption excites an electron (giving it energy) that can lead to side reactions. Some 
of these side reactions can create to free radicals (particles known to contribute to cancer) or damage 
DNA. In addition, because nanoparticles are so small, it may be easier for them to penetrate and circulate 
throughout the body. 

The biggest issue with nanoparticulate ingredients is not that they are necessarily more dangerous than 
other ingredients but that because they are new, they have not been fully researched yet. 

• SmartShopper's position on the use of sunscreens nanoparticulate ingredients (do you endorse their 
use?) with justification of this position based on a comparison of the benefits and risks involved. 

How to make a pamphlet 

It is up to you how "professional" you want your students to make their pamphlets. If you have two class 
periods or less to devote to this project, we suggest that you have your students focus on the content and 
produce "draft versions" of the pamphlet. 

By Hand: 

Take a regular piece of 8.5 x 11 paper turn it sideways. Fold the paper into thirds and crease it firmly. This 
is what the pamphlet will look like when it's done. When you unfold the paper, you can use the creases 
as column guides. It is good to make the front and back of your pamphlet on different pieces of paper and 

317 www.ckl2.org 



use a copying machine to make the pamphlet double sided in case you decide to make changes along the 
way. 

With a Computer: 

Open a new document in Microsoft Word. Go to File>Page Setup to choose a Landscape Orientation and 
make all of the margins 0.5 inches. Go to Format > Columns to choose 3 columns and click the check box 
for Line Between. You will need to either use a printer that will print double-sided or print the two sides 
of your pamphlet separately and use a copying machine to make them double sided. 



8.5 



Folded pumphlet 
Evaluation 

SmartShopper will evaluate the pamphlets based on the following criteria: 

• All required information is present and correct 

• Scientific explanations are used to back up pamphlets claims 

• Effective use of diagram and graph to enhance explanation of why nanoparticulate sunscreen ingre- 
dients are clear 

• Convincing argument weighing all the relevant information for position taken on nanoparticulate 
sunscreen use 

• All team member contributed and worked together to produce the animations 

See full rubric on the last page. 



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318 



Table 2.36: Rubric for Consumer Choice Pamphlet Evaluation 



Category 



Required Informa- 
tion 

• Overview of 
nanoingredi- 
ents 

• List of com- 
mon nanoin- 
gredients 

. How UV 

light is 

blocked and 
advantages 
over other 
blockers 

• Why nanoin- 
gredients are 
clear 

• Visible light 
scattering 
diagram 

• 

Transmission 
graph 

• Possible 
downsides 

• Position on 
use 



Novice (1) Ab- Apprentice (2) Skilled (3) Ade- Masterful (4) 

sent, missing or Partially devel- quately developed Fully developed 
confused oped 



0-1 parts of the re- 
quired information 
are present. 



2—4 parts of the re- 
quired information 
are present. 



5-7 parts of the re- 
quired information 
are present. 



All 8 parts of the 
required informa- 
tion are present. 



Pamphlet claims 
are backed up with 
accurate scientific 
explanations 



Few of the re- 
quired elements 
are accurately 

depicted. 

Few of the claims 
are backed up. 



Some of the re- 
quired elements 
are accurately 

depicted. 

Some of the claims 
are backed up. 



Most of the re- 
quired elements 
are accurately 

depicted. 

Most of the claims 
are backed up. 



All of the required 
elements are accu- 
rately depicted. 

All of the claims 
are backed up. 



319 



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Table 2.36: (continued) 



Category 



Transmission 
graph is correctly 
interpreted 

. % T is the 
correctly 
read from 
graph 

. % T cor- 
rectly re- 
lated to 1. 
Visible opac- 
ity, 2.UVA 
blocking and 
3. UVB 

blocking. 



Novice (1) Ab- Apprentice (2) Skilled (3) Ade- Masterful (4) 

sent, missing or Partially devel- quately developed Fully developed 
confused oped 



1 or none of the 
key aspects of the 
graph are correctly 
interpreted. 



2 of the key as- 
pects of the graph 
are correctly inter- 
preted 



3 of the key as- 
pects of the graph 
are correctly inter- 
preted 



All 4 key aspects of 
the graph are cor- 
rectly interpreted 



Effective use of di- 
agram to show vi- 
sual transparency 
of sunscreen 

• Diagram 
includes 
sun, pho- 
tons, skin, 
nanoparticle 
sunscreen, 
skin, and 
observer 

• No scatter- 
ing of visible 
light 

• Skin absorbs 
blue/green 
light 

• Observer 
sees 

red /yellow 
skin 



1 or none of the 
key aspects of the 
interaction are 

correctly shown. 



2 of the key as- 
pects of the in- 
teraction are cor- 
rectly shown. 



3 of the key as- 
pects of the in- 
teraction are cor- 
rectly shown. 



All 4 key aspects of 
the interaction are 
correctly shown. 



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320 



Table 2.36: (continued) 



Category 



Convincing ar- 
gument to sup- 
port position on 
nanoparticulate 
sunscreen use 

• Uses all 
available 
information 

• Information 
interpreted 
with re- 
spect to user 
concerns 

• Both pros 
and cons 
considered 

• Justification 
for position 
taken 



Novice (1) Ab- Apprentice (2) Skilled (3) Ade- Masterful (4) 

sent, missing or Partially devel- quately developed Fully developed 
confused oped 



0-1 key aspects of 
the argument are 
given effectively. 



2 key aspects of 
the argument are 
given effectively. 



3 key aspects of 
the argument are 
given effectively. 



All 4 key aspects of 
the argument are 
given effectively. 



Teamwork 



All team 
members 
contributed 
significantly 



to 

project 

Group 

worked 

gether 

manage 

problems 

a team 



the 

to- 

to 

as 



Few team mem- 
bers contributed 
to the project. 



Some team mem- 
bers contributed 
to the project. 



Most team mem- 
bers contributed 
to the project. 



All team members 
contributed to the 
project. 



Group did not ad- 
dress the problems 
encountered. 



Group did not 
manage problems 
effectively. 



Problems in the 
group managed by 
one or two individ- 
uals. 



Group worked 

together to solve 
problems. 



The Science Behind the Sunscreen Quiz: Teacher Answer Key 

1. Why is UV light a source of health concern when visible and infrared light are not? (2 points) 

321 www.ckl2.ors 



• UV light is a higher frequency light than visible and infrared and thus has a higher energy per photon. 

• This higher energy allows it to do damage even though the total amount of UV light reaching the 
earth is less than for visible and infrared light. 

2. List 2 kinds of damage to the body caused by UV radiation. (2 points) 
Any of the following four answers are acceptable. 

• Sunburn 

• Pre-mature skin aging 

• Skin cancer 

• Cataracts 

3. Explain in your own words why it is important to block UVA light. (2 points) 

• Even though it does not cause short-term damage like sunburns, UVA light has been found to cause 
long term damage including premature skin aging and skin cancer. 

• It is especially dangerous because it has been found to penetrate more deeply into the skin than UVB 
light and because the effects are not immediately apparent, we may not realize that damage is being 
done. 

4. How do you know if a sunscreen protects against UVA light (now and future)? (2 points) 

• Currently, the only way to tell how well a sunscreen protects against UVA rays is by looking at the 
ingredients and knowing which ones absorb UVA light. 

• A new FDA rating for UVA light based on a 4-star system should be implemented in the next few 
years (more stars will equal greater UVA protection). 

5. How do you know if a sunscreen protects against UVB light? (1 points) 

• A sunscreen's SPF (Sunburn Protection Factor) number indicates its ability to absorb UVB light (a 
higher number equals greater UVB protection). 

6. For each of the following absorption graphs, circle the correct answers for a) what kind(s) of light are 
strongly absorbed and b) whether it is an organic or inorganic sunscreen. (4 points) 

1.0 



■ 0.5 



-Q 
< 



0.0 




o 
CO 

-§0.5 
if) 

-Q 
< 



0.0 



200 250 300 350 400 

Wavelength(nm) 



200 250 300 350 400 

Wavelength(nm) 



a)|UVAl 



UVB 



b) |Organic] Inorganic 



a) lUVAl I UVB I 

b) Organic llnorganicl 



7. Why do sunscreens that use nano-sized 7702 clusters appear clear on our skin while sunscreens that use 
traditional sized T1O2 clusters appear white? (5 points) 



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322 



• Suspended clusters scatter light maximally for wavelengths twice as large as their diameter. 

• Since visible light has A « 400 - 800 nm, cluster with a diameter of 200 - 400 nm (such as traditional 
T1O2) scatter much visible light. 

• The scattered rays that are reflected towards our eyes are of all colors in the spectrum, making the 
sunscreen appear white. 

• Clusters smaller than 100 nm in diameter (such as nano T1O2) do not scatter appreciably in the 
visible range. 

• The visible light passes through the sunscreen and is reflected by our skin. Thus our skin color is 
what we see, making the nano-sized T1O2 particles effectively clear. 

8. How do you know if a sunscreen has "nano" ingredients? (2 points) 

• Contains inorganic ingredients (ZnO or TiO<i) 

• Sunscreen appears clear on the skin. 

9. Briefly describe one benefit and one drawback of using a sunscreen that contains "nano" ingredients: (1 
point each, a total of 2 points) 

Benefits (Either of the following answers is acceptable) 

• Block whole UV spectrum 

• Appear clear, people less likely to under apply 

Drawbacks (Either of the following answers is acceptable) 

• New chemicals not fully studied; possible harmful effects still unknown. FDA is not treating nano- 
versions of known chemicals as new; needed health studies may not occur. 

• Very small particles are more likely to cross membranes and get into unintended parts of the body 

10. In what ways are "nano" sunscreen ingredients similar and different from other ingredients currently 
used in sunscreens? For each of the four categories below, indicate whether "nano" sunscreen ingredients 
are "similar" or "different" to organic and inorganic ingredients and explain how. (1 point each, total of 8 
points) 

Table 2.37: 



Organic Ingredients (e.g. PABA) 



Inorganic Ingredients (e.g. Clas- 
sic Zinc Oxide used by lifeguards) 



Chemical Structure 



Kinds of Light Blocked 



Similar or Different 
How: Nano ingredients are small 
ionic clusters while organic ingre- 
dients are molecules. 

Similar or Different 

How: Organic ingredients each 
block a small part of the UV 
spectrum (generally UVB) while 
nano ingredients block almost 
the whole thing, 



Similar or Different 
How: Nano ingredients are a 
kind of inorganic ingredients. 
Bother are ionic clusters but the 
nano clusters are smaller. 
Similar or Different 
How: Both nano ingredients and 
traditional inorganic ingredients 
block almost the whole UV spec- 
trum. 



323 



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Table 2.37: (continued) 



Organic Ingredients (e.g. PABA) 



Inorganic Ingredients (e.g. Clas- 
sic Zinc Oxide used by lifeguards) 



Way Light is Blocked 



Appearance on the Skin 



Similar or Different 
How: Both nano and organic in- 
gredients block UV light via ab- 
sorption. (The specific absorp- 
tion mechanism is different, but 
students are not expected to re- 
port this) 

Similar or Different 
How: Both nano and organic 
ingredients appear clear on the 
skin. 



Similar or Different 

How: Both nano and inorganic 

ingredients block UV light via 

absorption. 



Similar or Different 
How: Traditional inorganic in- 
gredients appear white on the 
skin while nano ingredients ap- 
pear clear. 



Clear Sunscreen Final Reflections: Teacher Instructions &; Answer Key 

The goal of this exercise is for students to reflect on their learning and evaluate how their ideas and their 
confidence in them has changed since the unit began. The answers to the questions on page two are also a 
final check for you to see where students are and if they have any misconceptions that need to be addressed. 
Possible student answers are listed below, these are compiled based on completion of the entire unit. If 
you have only done selected lessons with your class, some of the answers many not apply. Please refer to 
the teacher's version of the reflection sheets associated with each lesson for lesson- specific answers. 

Now that you have come to the end of the unit, go back and look at the reflection forms you filled out after 
each activity and try to answer the guiding questions below. Write down answers each question below and 
then evaluate how confident you feel that each idea is true. 

Table 2.38: 



1. What are the 
most important 

factors to consider 
in choosing a sun- 



How sure are you 
that this is true? 

Not to Sure 



How sure are you 
that this is true? 

Kind-of Sure 



How sure are you 
that this is true? 

Very Sure 



It is important to choose 
a sunscreen that pro- 
vides good protection 
against both UVA and 
UVB. 

A sunscreen 's SPF num- 
ber tells us how well 
the sunscreen protects 
against UVB rays. 



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324 



Table 2.38: (continued) 



1. What are the 
most important 

factors to consider 
in choosing a sun- 



How sure are you 
that this is true? 

Not to Sure 



How sure are you 
that this is true? 

Kind-of Sure 



How sure are you 
that this is true? 

Very Sure 



For UVA protection, 
until the new FDA 
rating is approved, 
the only way to tell 
how well a sunscreen 
protects against UVA 
rays is by looking at the 
ingredients. 

Inorganic ingredients 
(ZnO and TiOq) absorb 
both UVA and UVB, so 
sunscreens that include 
them have broadband 
protection. 

Organic ingredients 

each block a specific 
wavelength range that 
can be in the UVA or 
UVB range. To ensure 
broadband protection, 
it is important to 
choose a sunscreen that 
has a combination of 
ingredients that will 
absorb both kinds of 
light. Avobenzone and 
Ecamsule are the two 
FDA approved organic 
ingredients that absorb 
strongly across the 
UVA range. 

It is also important to 
choose a sunscreen that 
we like in terms of ap- 
pearance and smell to 
make sure that we use 
enough of it to be effec- 
tive. 



325 



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Table 2.39: 



2. How do you know 
if a sunscreen has 
"nano" ingredients? 



How sure are you 
that this is true? 

Not to Sure 



How sure are you 
that this is true? 

Kind-of Sure 



How sure are you 
that this is true? 

Very Sure 



"Nano" ingredients are 
smaller versions of tra- 
ditional inorganic ingre- 
dients (ZnO and 7702) 
that go on clear. 
If a sunscreen contains 
Zinc Oxide or Titanium 
Dioxide, but appears 
clear on our skin, then it 
likely contains nanopar- 
ticles of ZnO or 7702- 
Traditional ZnO and 
7702 clusters appear 
white because they are 
> 200 nm in diame- 
ter and thus scatter 
all colors of visible 
light back towards 
our eyes. (Maximum 
scattering occurs at 
A = 2 * diameter). 
ZnO and 7702 nanopar- 
ticles are < 100 nm 
in diameter and thus 
do not scatter apprecia- 
bly in the visible range. 
The visible light passes 
through the sunscreen 
and is reflected by our 
skin, thus the sunscreen 
appear clear. 



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326 



Table 2.40: 



3. How do "nano" How sure are you How sure are you How sure are you 
sunscreen ingredi- that this is true? that this is true? that this is true? 

ents differ from most Not to Sure Kind-of Sure Very Sure 



other ingredients 

currently used in 
sunscreens? 



Most ingredients 

currently used in sun- 
screens are organic 
ingredients. These are 
individual molecules 
that absorb narrow 
bands of the UVA or 
UVB spectrum. 
"Nano" sunscreen ingre- 
dients are inorganic and 
very similar to tradi- 
tional inorganic ingre- 
dients (large ZnO and 
7702 clusters) ■ they 
are made up of the 
same kinds of atoms and 
have the same formula 
unit, thus they absorb 
strongly in both the 
UVA and UVB range 
up to their cutoff wave- 
length: 380 nm [ZnO) 
or 365 nm (Ti02)- 
However, because the 
nano inorganic clusters 
are much smaller in size 
than traditional inor- 
ganic ones (< 100 nm 
in diameter as op- 
posed to > 200 nm), 
they don't scatter vis- 
ible light (maximum 
scattering occurs at 
A = 2 * diameter) and 
thus appear clear on 
our skin. 



Now go back to the worksheet you filled out with your initial ideas at the beginning of the unit and mark 
each idea with a V if you still believe it is true, an X if you don't think that it is true and a ? if you are 
still unsure. Then answer the following questions. 

1. What ideas do you have now that are the same as when you started? 



327 www.ckl2.org 



2. What ideas are different and how? 

3. What things are you still unsure about? 

One-Day Version of Clear Sunscreen 
Teacher Lesson Plan 

Contents 

• One-Day Version of Clear Sunscreen: Teacher Lesson Plan 

• NanoSunscreen: The Wave of the Future?: PowerPoint Slides and Teacher Notes 

Orientation 

This abridged version of the Clear Sunscreen unit provides a one-day overview of the science behind 
nanosunscreens for teachers with limited time. This version is specifically designed for students who have 
a significant background in chemistry, physics and biology; while it covers a large amount of content, most 
of the ideas and concepts presented should be familiar to students from their other science classes. 

The goal of this lesson is to give student an overview of the dangers of sun radiation, how sunscreens 
work to protect us, and what determines how they appear on our skin, with a focus on the particular case 
of nanosunscreens. The lesson is structured around a central PowerPoint, and has a demonstration, an 
animation, and several student handouts to support learning. 

• The NanoSunscreen - The Wave of the Future? PowerPoint starts by explaining the dangers of sun 
radiation and the need to use sunscreen to protect our bodies. A brief introduction to the different 
kinds of electromagnetic waves and their energies sets the stage for differentiating between the two 
kinds of UV light that we need to protect our bodies from (UVA and UVB). The PowerPoint then 
takes students through the history of why sunscreens were first developed, their current rating system 
for UVB blocking ability (SPF) and the need to also consider UVA blocking ability. Next, the slides 
explore the different structure and blocking mechanisms of organic and inorganic sunscreen ingre- 
dients. Finally the slides discuss what gives inorganic sunscreens their "white" or clear appearance 
and how the nano versions remedy this situation. 

• There is an optional demonstration of absorption of UV light by chemicals in printed money (as an 
anti-counterfeiting measure) embedded in the PowerPoint presentation that you can do with your 
class. 

• There is an optional animation that illustrates the process of how UV and visible light interacts 
with sunscreen and our skin. This animation can be downloaded from the NanoSense website at 
http : //nanosense . org/activities/clearsunscreen/index . html . 

• Three Student Handouts are provided to support the concepts introduced in the PowerPoint. 

Essential Questions (EQ) 

What essential questions will guide this unit and focus teaching and learning? 

• What are the most important factors to consider in choosing a sunscreen? 

• How do you know if a sunscreen has "nano" ingredients? 

• How do "nano" sunscreen ingredients differ from most other ingredients currently used in sunscreens? 

Enduring Understandings (EU) 

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Students will understand: 

(Numbers correspond to learning goals overview document) 

1. How the energies of different wavelengths of light interact differently with different kinds of matter. 

2. Why particle size can affect the optical properties of a material. 

3. That there may be health issues for nanosized particles that are undetermined at this time. 
6. How to apply their scientific knowledge to be an informed consumer of chemical products. 
Key Knowledge and Skills (KKS) 

Students will be able to: 

(Numbers correspond to learning goals overview document) 

1. Describe the mechanisms of absorption and scattering by which light interacts with matter. 

2. Describe how particle size, concentration and thickness of application affect how particles in a sus- 
pension scatter light. 

3. Explain how the phenomenon of seeing things in the world is a human visual response depending on 
how light interacts with objects. 

4. Evaluate the relative advantages (strong blockers, UVA protection) and disadvantages (possible car- 
cinogenic effects, not fully researched) of using nanoparticulate sunscreens. 



329 www.ckl2.org 



Table 2.41: Timeline 



Day 



Activity 



Time 



Materials 



Day 1 (50 min) 



Show NanoSunscreen 
The Wave of the 
Future? PowerPoint 
Slides, using the ques- 
tion slides and teacher's 
notes to start class 
discussion. 

Perform Demonstration 
associated with Power- 
Point Presentation (op- 
tional) . 

Show Animation asso- 
ciated with PowerPoint 
Presentation (optional) . 
Give out student hand- 
outs and discuss as at 
appropriate parts of the 
presentation: 

• Sun Radiation 
Summary 

• Summary of FDA 
Approved Sun- 
screen Ingredients 

• Overview of Sun- 
screen Ingredients 



50 min 



NanoSunscreen The 
Wave of the Future? 
PowerPoint Slides & 
Teacher Notes 
Computer and projector 
Optional Demonstra- 
tion Materials: UV 
light, different kinds of 
paper currency. 
Optional Anima- 

tion: Download from 
http : //nanosense . 
org/activities/ 
clear sunscreen/ 
index . html 

Copies of Student 
Handouts 



NanoSunscreen 




The Wave of the Future? 



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330 



Parti 

Understanding the Danger 

Why use sunscreen? 

Too Much Sun Exposure is Bad for Your Body 




• Premature skin aging (wrinkles) 

• Sunburns 

• Skin cancer 

• Cataracts 

Skin Cancer Rates are Rising Fast 

Skin cancer: 



Figure 2.83 



331 



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332 



Probability of getting skin cancer 



1930 : 


: 1 


in 


5,00 


2004 : 


: 1 


in 


65/ 


205' 


1 


in 


>n... 




Figure 2.85 



333 



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• ~ 50% of all cancer cases 

• > 1 million cases each year 

• ~ 1 person dies every hour 

Causes of the increase: 

• Decrease ozone protection 

• Increased time in the sun 

• Increased use of tanning beds 

What are sun rays? 

How are they doing damage? 

The Electromagnetic Spectrum 

• Sun rays are electromagnetic waves 

— Each kind has a wavelength, frequency and energy 



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Figure 2.86 



The Sun's Radiation Spectrum I 



The sun emits several kinds of electromagnetic radiation 
- Infrared (IR), Visible (Vis), and Ultra Violet (UV) 

Higher energy radiation can damage our skin 



The Sun's Radiation Spectrum II 

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334 




Figure 2.87 



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< 




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Wavelength of Light (k) in nm 
Higner Energy 



Figure 2i 



335 



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• How much UV, Vis & IR does the sun emit? 

How can the sun's rays harm us? 
Sun Rays are Radiation 




Figure 2.89 

Light radiation is often thought of as a wave with a wavelength (/t) and frequency (/) related by this 
equation: 

C = Axf 

Since c (the speed of light) is constant, the wavelength and frequency are inversely related 



'-7 



'=* 



• This means that light with a short wavelength will have a high frequency and visa versa 

Radiation Energy I 

En 
Eocf 




1. Energy Comes in Packets 
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336 



The size of an energy packet (E) is determined by the frequency of the radiation (/) 

E = hxf 

Radiation with a higher frequency has more energy in each packet 

The amount of energy in a packet determines how it interacts with our skin 



Radiation Energy II 



UV INDEX 




Figure 2.90 



2. Total Energy 



• This relates not only to how much energy is in each packet but also to the total number of packets 
arriving at a given location (such as our skin) 

• Total Energy depends on many factors including the intensity of sunlight 

• The UV Index rates the total intensity of UV light for many locations in the US daily: http: 
//www . epa . gov/sunwise/uvindex . html 

Skin Damage I 



The kind of skin damage is determined by the size of the energy packet (E = h* f) 
The UV spectrum is broken into three parts: 

337 



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Figure 2.91 

- Very High Energy (UVC) 

- High Energy (UVB) 

- Low Energy (UVA) 

• As far as we know, visible and IR radiation don't harm the skin 
Skin Damage II 

• Very high energy radiation (UVC) is currently absorbed by the ozone layer 

• High energy radiation (UVB) does the most immediate damage (sunburns) 

• Lower energy radiation (UVA) can penetrate deeper into the skin, leading to long term damage 



Sun Radiation Summary I 



Table 2.42: Sun Radiation Summary II 



Radiation 


Characteristic 


Energy per 


% of Total Ra- 


Effects on Hu- 


Visible to Hu- 


Type 


Wavelength 


Photon 


diation Emit- 
ted by Sun 


man Skin 


man Eye? 




Increasing 


Decreasing 










wavelength 


Energy 








UVC 


~ 200 - 290 nm 

(Short-wave 

UV) 


High Energy 


~ 0% (< 1% of 
all UV) 


DNA Damage 


No 


UVB 


~ 290 - 320 nm 


Medium En- 


~ .35% (5% of 


Sunburn DNA 


No 




(Mid-range 


ergy 


all UV) 


Damage Skin 






UV) 






Cancer 




UVA 


320 - 400 nm 


Low Energy 


~ 6.5% (95% of 


Tanning Skin 


No 




(Long-wave 




all UV) 


Aging DNA 






UV) 






Damage Skin 
Cancer 




Vis 


~ 400 - 800 nm 


Lower Energy 


-43% 


None Cur- 
rently Known 


Yes 


IR 


800 - 
120, 000 nm 


Lowest Energy 


-49% 


Heat Sensation 
(high A IR) 


No 



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Protecting Ourselves 
What do Sunscreens Do? 



338 



Penetration of Different Wavelengths 
of Light into Human Skin 



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layert 

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Figure 2.92: N.A. Shaath. The Chemistry of Sunscreens. In: Lowe NJ, Shaath NA, Pathak MA, editors. 
Sunscreens, development, evaluation, and regulatory aspects. New York: Marcel Dekker; 1997. p. 263-283. 



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Higner Energy 



Figure 2.93 



339 



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Figure 2.94 



Total 

Incoming Light Absorbed Light 




Reflected Light 



Transmitted Light 



Figure 2.95 



Transmission 

Reflection 

+ Absorption 

100% 



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340 



• If we say that light is "blocked" it means that it is either absorbed or reflected by the material 

— Sunscreens mainly block via absorption 

A Brief History of Sunscreens: The Beginning 

• First developed for soldiers in WWII (1940s) to absorb "sunburn causing rays" 




280 320 
Wavelength 






WWII soldiers 
in the sun 



The sunburn causing rays 
were labeled as UV-B 



Longer wavelengths in the 
UV range were called UV-A 



Figure 2.96 
A Brief History of Sunscreens: The SPF Rating 

• Sunscreens first developed to prevent sunburn 

— Ingredients were good UVB absorbers 

• SPF Number (Sunburn Protection Factor) 

— Measures the strength of UVB protection only 

— Higher SPF jf= = more protection from UVB 

— Doesn't tell you anything about protection from UVA 

A Brief History of Sunscreens: The UVA Problem 

• UVA rays have no immediate visible effects but cause serious long term damage 

— Cancer 

— Skin aging 

• Sunscreen makers working to find UVA absorbers 



341 



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30 



• <•-««* Mt 



Figure 2.97 



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342 




Twenty different skin cancer lesions 

Figure 2.98 

• NEW: The FDA has just proposed a 4-star UVA rating to be included on sunscreen labels! 

Low* * •• Med* • •• High* • •• Highest* • •• 

How do you know if your sunscreen is a good UVA blocker? 




Figure 2.99 
Know Your Sunscreen: Look at the Ingredients 

• UV absorbing agents suspended in a lotion 

— "Colloidal suspension" 

• Lotion has "inactive ingredients" 



343 



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I = Lotion 



=Active Ingredients 



Figure 2.100 

— Don't interact w/ UV light 

UV absorbing agents are "active ingredients" 

— Usually have more than one kind present 
Two kinds of active ingredients 

— Organic ingredients and inorganic ingredients 



Table 2.43: Sunscreen Ingredients Overview 



Organic Ingredients 



Inorganic Ingredients 



Atoms Involved 

Structure (not drawn to scale) 



Carbon, Hydrogen, Oxygen, Ni- Zinc, Titanium, Oxygen 

trogen 

Individual molecule 

title 



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344 



Table 2.43: (continued) 



Organic Ingredients Inorganic Ingredients 



i3» 



Absorb specific bands of UV light Absorb all UV with A < critical 

value 




•1 






UV Blocking 

Appearance Clear Large clusters = White Small 

clusters = Clear 

Organic Ingredients: The Basics 

• Organic = Carbon Compounds 

— H,0 & N atoms often involved 

• Structure 

345 www.ckl2.org 



Octyl methoxycinnamate (C 18 H 26 3 ) 
an organic sunscreen ingredient 




Figure 2.101 



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346 



— Covalent bonds 

— Exist as individual molecules 

• Size 

— Molecular formula determines size (states the number and type of atoms in the molecule) 

— Typically a molecule measures a few to several dozen A (< 10 nm) 

Organic Ingredients: UV Blocking 



incoming 
UV radiation 



Outgoing 
IR radiation 




Excitad 

Mottcult 



Figure 2.102 

1. Molecules capture energy from the sun's UV rays 

2. The energy give the molecule thermal motion (vibrations and rotations) 

3. The energy is reemitted as harmless long wave IR 

Organic Ingredients: Absorption Range 

• Organic molecules only absorb UV rays whose energy matches the difference between the molecule's 
energy levels 

— Different kinds of molecules have different peaks and ranges of absorption 

— Using more than one kind of ingredient (molecule) gives broader protection 




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Figure 2.103 
Organic Ingredients: Absorbing UVA / UVB 

347 



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Most organic ingredients that are currently used were selected because they absorb UVB rays 

— The FDA has approved 15 organic ingredients 

— 13 of these primarily block UVB rays 

Sunscreen makers are working to develop organic ingredients that absorb UVA rays 

— Avobenzone and Ecamsule are good FDA approved UVA absorbers 




Figure 2.104 

How are inorganic sunscreen ingredients different from organic ones? 
How might this affect the way they absorb UV light? 
Inorganic Ingredients: The Basics 

• Atoms Involved 

— Zinc or Titanium 

— Oxygen 

• Structure 

— Ionic attraction 

— Cluster of ions 

— Formula unit doesn't dictate size 

• Size 

— Varies with # of ions in cluster 

— Typically ~ 10 nm - 300 nm 

Inorganic Ingredients: Cluster Size 

• Inorganic ingredients come in different cluster sizes (sometimes called "particles") 

— Different number of ions can cluster together 

— Must be a multiple of the formula unit 

— ZnO always has equal numbers of Zn and O atoms 

— 7702 always has twice as many O as Ti atoms 

Inorganic Ingredients: UV Blocking 

• Inorganic Sunscreen Ingredients can also absorb UV rays 
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Detail of the ions in 
one cluster 




Group of Ti0 2 particles 



Figure 2.105 




Two 

Ti0 2 particles 




~100 nm 



-200 nm 



Figure 2.106 



349 



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Inorganic Compound Absorption 

A 

m 
u 

c 
n 

"£o.s 

o 
< 



o.c 



?0.n 250 300 350 40C 

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Figure 2.107 

— But a different structure leads to a different absorption mechanism 

— Absorb consistently through whole UV range up to ~ 380 nm 

— How is the absorption pattern different than for organics? 

If inorganic sunscreen ingredients block UVA light so well, why doesn't everybody use them? 




Figure 2.108 



Appearance Matters 



• Traditional inorganic sunscreens appear white on our skin 
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Figure 2.109 

• Many people don't like how this looks, so they don't use sunscreen with inorganic ingredients 

• Of the people who do use them, most apply too little to get full protection 

Why Do They Appear White? I 




Figure 2.110 

351 



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Traditional ZnO and 7702 clusters are large 

- (> 200 nm) 

Large clusters can scatter light in many different directions 

Maximum scattering occurs for wavelengths twice as large as the cluster 

- A > 400 nm 

- This is visible light! 



Why Do They Appear White? II 

Light eventually goes in one of two directions: 



Back Scattering 

-V 



"""~c o \ ?/f ° 



o o 



°" \ o 

o o 






\ 



T 



I - nt Scattering 



Figure 2.111 

• Back the way it came (back scattering) 

— Back-scattered light is reflected 

• Forwards in the same general direction it was moving (front scattering) 

— Front-scattered light is transmitted 

Why Do They Appear White? Ill 

• When reflected visible light of all colors reaches our eyes, the sunscreen appears white 

• This is very different from what happens when sunlight is reflected off our skin directly 

— Green/blue rays absorbed 

— Only red/brown/yellow rays reflected 



Why don't organic sunscreen ingredients scatter visible light? 
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Figure 2.112 



353 



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Figure 2.113 




r 



200 nm TiO ; particle 
(Inorganic) 



Methoxycinnamate (<10 nm) 
(Organic) 



Figure 2.114 




( 




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Figure 2.115 

354 



Organic Sunscreen Molecules are Too Small to Scatter Visible Light 

What could we do to inorganic clusters to prevent them from scattering visible light? 

Nanosized Inorganic Clusters I 

• Maximum scattering occurs for wavelengths twice as large as the clusters 

— Make the clusters smaller (100 nm or less) and they won't scatter visible light 



\ 




/ 


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o o O 

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° o 

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o o o 

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Figure 2.116 



Nanosized Inorganic Clusters II 



Maximum scattering occurs for wavelengths twice as large as the clusters 

— Make the clusters smaller (100 nm or less) and they won't scatter visible light 



Nano- Sunscreen Appears Clear 



Table 2.44: In Summary I 



Organic Ingredients Inorganic Ingredients (Narlcflbrganic Ingredients (Large) 

Structure Individual molecule Cluster ~ 100 nm in di- Cluster > 200 nm in di- 
ameter ameter 
Interaction w/UV light Absorb specific A of UV Absorb all UV < critical Absorb all UV < critical 

light A A 

Absorption Range Parts of UVA or UVB Broad spectrum, both Broad spectrum, both 

spectrum UVA and UVB UVA and UVB 

Interaction w/Vis light None None Scattering 

Appearance Clear Clear White 



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Scattering for 100 nm and 200 nm ZnO clusters 




200 260 300 360 400 450 600 

Wavelength (nm) 

Figure 2.117 



Nanosized ZnO 
particles 



Large ZnO 
particles 




Figure 2.118 



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356 



In Summary II 

• Nanoparticle sunscreen ingredients are small inorganic clusters that: 

— Provide good UV protection by absorbing most UVB and UVA light 

— Appear clear on our skin because they are too small to scatter visible light 




Figure 2.119 



NanoSunscreen: The Wave of the Future?: Teacher Notes 

Overview 

This series of interactive slides cover the basic science for how nanosunscreens work, including: 

• The dangers of UV radiation and our need to protect ourselves against them 

• The history of sunscreens and the different types available 

• How sunscreens absorb UV light and what determines which wavelengths are absorbed 

• How scattering of visible light by sunscreen determines if they appear white or clear 

Slide 29 includes an optional demo that shows how selective absorption of UV light by certain chemicals 
used in printing money is serves as an anti-counterfeiting measure. If you choose to do this demo you will 
need: 



One or more UV lights of any size (several options are available from Educational Innovations at 
www . teachersour ce .com) 

Different kinds of paper currency (these must be relatively recently printed; Euros and Canadian 
bills work particularly well) 



357 



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Slide 43 includes an optional animation to illustrate the process of how UV and visible light interacts 
with sunscreen and our skin. This animation can be downloaded from the NanoSense website at http: 
//nanosense. org/activities/clearsunscreen/index.html. 

Three Student Handouts are provided to support the concepts introduced in the PowerPoint. These can 
be given out at any point, but relevant slide suggestions are given: 



Sun Radiation Summary (Slides 16/17) 

Summary of FDA Approved Sunscreen Ingredients (Slide 30) 

Overview of Sunscreen Ingredients (Slide 26 or 46) 



Slide 1: Title Slide 

Questions for Students: Do you wear sunscreen? Why or why not? Are there nanoparticles in your 
sunscreen? How do you know? 

Slide 2: Part 1 — Understanding the Danger (Section Header) 
Slide 3: Why use sunscreen? (Question Slide) 

Have your students brainstorm ideas about why it is important to use sunscreen. 

Slide 4: Too Much Sun Exposure is Bad for Your Body 

This slide describes the three main dangers of UV radiation: 

• Premature skin aging leads to leathery skin, wrinkles and discolorations or "sun spots". Eyes can also 
be damaged by UV radiation leading to cataracts (damage to the eyes which causes cloudy vision). 

• Sunburns are not only painful but are also a distress response of the skin giving us a signal that 
damage is being done. 

• Skin cancer occurs when UV rays damage DNA in skin cells leading to genetic mutations. The 
mutated cells grow and divide uncontrollably forming a tumor. If caught early, the cancer can be 
removed; otherwise it can spread to other parts of the body and eventually cause death. 

Slide 5: Skin Cancer Rates are Rising Fast 

This slide describes the most dangerous consequence of UV radiation - skin cancer. 

It is only recently that being tan came into fashion and that people began to spend time in the sun on 
purpose in order to tan. In addition, clothing today generally reveals more skin than it did in the past. 

The use of tanning beds is not safe and a "base tan" only provides protection of about SPF 4. 

Discussion Question for Students: Are there any other reasons that skin cancer rates might be rising? 

Answer: Improvements in detection technology may mean that we identify more cases inflating the slope 
of the rise. 

Slide 6: What are sun rays? How are they doing damage? (Question Slide) 

Have your students brainstorm ideas about what sun rays are and how they interact with our body. 

Slide 7: The Electromagnetic Spectrum 

Note: The illustrations of the waveforms at the extremes of the wavelength/energy spectrum are not to 
scale. They are simply meant to be a graphical representation of longer and shorter wavelengths. 

www.ckl2.org 358 



You may want to discuss some of the properties and uses of the different parts of the electromagnetic 
spectrum further with your students: 

• Gamma rays result from nuclear reactions and have a very high frequency and energy per photon 
(very short wavelength). Because they have a high energy, the photons can penetrate into cell nuclei 
causing mutations in the DNA. 

• X-rays are produced in collision of high speed electrons and have a high frequency and energy per 
photon (short wavelength). Because they have a smaller energy than gamma rays, the x-ray photons 
can pass through human soft tissue (skin and muscles) but not bones. 

• Ultra Violet Light is produced by the sun and has a somewhat high frequency and energy per photon 
(somewhat short wavelength). Different frequencies of UV light (UVA, UVB) are able to penetrate 
to different depths of human skin. 

• Visible Light is produced by the sun (and light bulbs) and has a medium frequency and energy per 
photon (medium wavelength). Visible light doesn't penetrate our skin, however our eyes have special 
receptors that detect different intensities (brightnesses) and frequencies (colors) of light (how we see). 

• Infrared Light is emitted by hot objects (including our bodies) and have a low frequency and energy 
per photon (long wavelength). Infrared waves give our bodies the sensation of heat (for example 
when you stand near a fire or out in the sun on a hot day.) 

• Radio Waves are generated by running an alternating current through an antenna and have a very 
low frequency and energy per photon (very long wavelength). Because they are of such low energy 
per photon, they can pass through our bodies without interacting with our cells or causing damage. 

Slide 8: The Sun's Radiation Spectrum I 

Sun rays are a form of electromagnetic radiation. Electromagnetic radiation is waves of oscillating electric 
and magnetic fields that move energy through space. 

Discussion Question for Students: What is the difference between UVA, UVB and UVC light? 

Answer: They have different wavelengths, frequencies (UVC: ~ 100-280 nm; UVB: ~ 280-315 nm; UVC 
~ 315 - 400 nm) and thus different energies. 

Note: The division of the UV spectrum (as well as the division of UV, visible, infrared etc.) is a catego- 
rization imposed by scientists to help us think about the different parts of the electromagnetic spectrum, 
which is actually a continuum varying in wavelength and frequency. 

Slide 9: The Sun's Radiation Spectrum II 

The sun emits primarily UV, visible and IR radiation. < 1% of the sun's radiation is x-rays, gamma waves, 
and radio waves. 

The amount of each kind of light emitted by the sun is determined by the kinds of chemical reactions 
occurring at the sun's surface. 

You may want to point out to students that not all of the sun's radiation reaches the earth. 

There are several layers of gases surrounding the earth, called its atmosphere, which absorb some of this 
radiation 

• Water vapor (H2O) absorbs IR rays 

• Ozone (O3) absorbs some UV rays 

• Visible rays just pass through 

As the ozone layer is depleted, more of the UV light emitted by the sun will reach the earth. 
Slide 10: How can the sun's rays harm us? (Question Slide) 

359 www.cki2.0rg 



Have your students brainstorm ideas about how sun rays might interact with our body. What part(s) of 
our body do they interact with? How do they affect them? 

Slide 11: Sun Rays are Radiation 

If students are not already familiar with the concept of wavelength, it may help to draw a wave on the 
board and indicate that the wavelength is the distance between peaks. 

X 




The speed of light in a vacuum is always the same for all wavelengths and frequencies of light, (c = 
300,000,000 m/s) 

You may wish to point out to students that the letter 'c' is the same c in the famous E = mc 2 equation 
showing the relationship between matter and energy. 

You may also want to discuss the concept that all light travels at the same speed in the same medium and 
that this does not depend on the frequency or wavelength of the wave. For example, in other mediums 
(e.g. air, water) light travels slower than in a vacuum. The speed of all light in water is ~ 225, 563, 909 m/s 
(only 75% of speed in a vacuum.) 

Slide 12: Radiation Energy I 

Example: Imagine that you are outside your friend's window trying to get their attention. You can throw 
small pebbles at the window one after another for an hour and it won't break the window. On the other 
hand, if you throw a big rock just once, you will break the window. It doesn't matter if all the pebbles 
put together would be bigger and heavier than the one rock; because their energy is delivered as separate 
little packets, they don't do as much damage. The same is true with energy packets. 

h is Planck's constant (6.26 x 10~ 34 J s) 

Slide 13: Radiation Energy II 

Total Energy can not be predicted by the frequency of light. 

You may want to talk with your students about the different things that the total energy depends upon. 
For example: time of day (10am-2pm is the most direct and strongest sunlight), time of year, amount of 
cloud cover (though some UV always gets through), altitude. 

You may want to explore the UV index site with your students and look at how the index varies by location. 

Slide 14: Skin Damage I 

Discussion Question for Students: Which kinds(s) of UV light do you think we are most concerned 
about and why? 

Answer: The theoretical answer would be UVC>UVB>UVA in terms of concern because of energy packet 
size. This is true for acute (immediate) damage, though as shown in next slide, UVA has now been found 
to cause damage in the long term. UVC is currently not a major concern because it is absorbed by the 
atmosphere and thus doesn't reach our skin. 

Slide 15: Skin Damage II 

Premature aging is caused by damage to the elastic fibers (collagen) in the dermal layer of the skin. Because 

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UVA radiation has a lower frequency and thus lower energy per photon, it is not absorbed by the cells of 
the top layer of the skin (the epidermis) and can penetrate deeper into the skin (to the dermis) where it 
does this damage. 

Both UVA and UVB can enter the cell nucleus and cause mutations in the DNA leading to skin cancer. 

Most of the rapid skin regeneration occurs in the epidermal layer. The dermal layer does not regenerate 
as quickly and thus is subject to long term damage. 

Slide 16: Sun Radiation Summary I 

This slide and the following one sum up the differences between the different kinds of radiation emitted by 
the sun. There is a corresponding student handout that students can use as a quick reminder during the 
course of the unit. 

This graph contains the all the information about wavelength, frequency, energy and amount of each kind of 
radiation emitted by the sun. Note that the different "kinds" of radiation are really points on a continuum. 

Common Misconception: We see "black light" (UVA light) because it is close to the visible spectrum. 

The Real Deal: If that were true, we would be able to see all objects as bright under black light and 
that doesn't happen. For example at a party only certain clothes appear bright. What actually happens 
is that black light causes some materials to fluoresce or phosphoresce meaning they absorb the UVA light 
and re-emit violet light in the visible spectrum that our eyes can detect. 

Slide 17: Sun Radiation Summary II 

This slide and the previous one sum up the differences between the different kinds of radiation emitted by 
the sun. There is a corresponding student handout that students can use as a quick reminder during the 
course of the unit. 

This chart summarizes the all the information from the previous graph and lists the effects of each kind of 
radiation on the human body. 

Note: Different diagrams may have different cutoffs for the divisions between UVA, UVB, UVC, visible 
and IR. This is because the electromagnetic spectrum is a continuum and the divisions between categories 
are imposed by scientists, thus not always well agreed upon. 

Example: What determines if it is a "warm" versus a "hot" day? If you set the cutoff at 80 degrees 
Fahrenheit does that mean that a change from 79° ,F to 81° F is more meaningful than a change from 77° F 
to 79°F? 

Slide 18: Part 2 — Protecting Ourselves (Section Header) 

Slide 19: What do Sunscreens Do? 

This slide is designed to get students thinking about how sunscreens protect our skin. Have students 
brainstorm ideas about what might happen to the UV rays when they encounter the sunscreen. Ask them 
how they could test their ideas to see if they are correct. 

Slide 20: Light Blocking 

The T + R + A = 100% equation is based on the conservation of energy. All incoming light (energy) must 
be accounted for. It either passes through the material, is sent back in the direction from which it came 
or is absorbed by the material. 

Analogy: The R + T + A = 100% equation can be thought of in terms of baseball. When a pitcher throws 
the ball towards the batter, three things can happen. The batter can hit the ball (reflection), the catcher 
can catch the ball (absorption) , or the ball can pass by both of them (transmission) . 

A key point on this slide is that sunscreens block UV light by absorbing it. 



361 www.ckl2.org 



Slide 21: A Brief History of Sunscreens: The Beginning 

Sunscreens were developed to meet a specific and concrete need: prevent soldiers from burning when 
spending long hours in the sun. Scientists applied their knowledge of how light interacts with certain 
chemicals to develop products to meet this need. 

The division of the continuous UV spectrum into UVA and UVB categories is somewhat arbitrary. The 
UVB range is talked about as starting at around 280 - 290 nm at the lower end and ending around 
310 - 320 nm at the upper end. 

Slide 22: A Brief History of Sunscreens: The SPF Rating 

SPF (Sunscreen Protection Factor) values are based on an "in-vivo" test (done on human volunteers) that 
measures the redness of sunscreen- applied skin after a certain amount of sun exposure. 

SPF used to be thought of a multiplier that can be applied to the time taken to burn, but this is not done 
anymore because there are so many individual differences and other variables that change this equation 
(skin type, time of day, amount applied, environment, etc.) 

The FDA recommends always using sunscreens with an SPF of at least 15 and not using sunscreen as a 
reason to stay out in the sun longer. Remind students that no sunscreen can prevent all possible skin 
damage. 

Common Student Question: Is it true that sunscreens above SPF 30 don't provide any extra protection? 

Answer: No, this is not true. However, since SPF is not based on a linear scale, a sunscreen with an SPF 
of 40 does not provide twice as much protection as a sunscreen with an SPF of 20. Even though you don't 
get double the protection, you do get some additional protection and so there is added value in using SPFs 
above 30. 

In the past the FDA only certified SPFs up to 30 but didn't confirm the reliability of higher claims by 
sunscreen manufacturers. Recently, due to improvement in testing procedures, the FDA had proposed 
certifying results up to and SPF of 50. 

Slide 23: A Brief History of Sunscreens: The UVA Problem 

Since there is no immediate visible effect, it is relatively recently that we have come to understand the 
dangers of UVA rays. In August 2007, the FDA proposed a UVA rating to be included on sunscreen labels; 
as of December 2007, the proposal was still under discussion. If the FDA proposal is passed, sunscreen 
manufacturers will have 18 months to comply with the new labeling requirements. 

Creating a rating for UVA protection has been difficult for two reasons: 

1. Since UVA radiation does not lead to immediate visible changes in the skin (such as redness) what 
should be the outcome measure? Is it valid to do an "in-vitro" (in a lab and not on a human) test? 
(The FDA proposal includes both) 

2. How should the UVA protection level be communicated to consumers without creating confusion 
(with the SPF and how to compare / balance the two ratings)? (The FDA proposal uses a 4-star 
system) 

Creating a UVA blocking rating is important since without immediate harmful effects, people are not likely 
to realize that they have not been using enough protection until serious long term harm has occurred. 

Slide 24: How do you know if your sunscreen is a good UVA blocker? (Question Slide) 

Have your students brainstorm ideas about ways to tell if a sunscreen is a good UVA blocker. 
Slide 25: Know Your Sunscreen: Look at the Ingredients 

"Formulating" a sunscreen is the art of combing active and inactive ingredients together into a stable cream 

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or gel product. One of the important challenges here is creating a stable suspension with even ingredient 
distribution. If the active ingredients clump together in large groups then the sunscreen provides strong 
protection in some areas and little protection in others. 

Analogy: Students may be familiar with the suspension issue as it relates to paint. If paint has been 
sitting for a while and it is used directly, a very uneven color is produced. This is why we stir (or shake) 
paint before using in order to re-suspend the particles. 

Another issue in sunscreen formulation is trying to create a product that customers will want to buy and 
use. Qualities such as smell, consistency and ease of rubbing into the skin all play a role in whether or not 
a sunscreen will be used and whether it will be used in sufficient quantity. 

Slide 26: Sunscreen Ingredients Overview 

This slide is an advance organizer for the content of the rest of the slide set. You may wish to give your 
students the Overview of Sunscreen Ingredients: Student Handout at this point to refer to during the rest 
of the presentation. 

You do not need to discuss the details of each cell at this point in the presentation, simply point out that 
organic and inorganic ingredients have several different properties that will be discussed. All of the content 
of the table is explained in detail in the following slides. 

Slide 27: Organic Ingredients: The Basics 

The full name of the compound shown is octyl methoxycinnamate (octyl refer to the eight carbon hy- 
drocarbon tail shown on the right side of the molecule) but it is commonly referred to as octinoxate or 
OMC. 

Slide 28: Organic Ingredients: UV Blocking 

When a molecule absorbs light, energy is converted from an electromagnetic form to a mechanical one (in 
the form of molecular vibrations and rotations). Because of the relationship between molecular motion 
and heat, this is often referred to as thermal energy. 

The process of releasing the absorbed energy is called relaxation. While atoms which have absorbed 
light simply re-emit light of the same wavelength/energy, molecules have multiple pathways available for 
releasing the energy. Because of the many vibrational and rotational modes available, there are many 
choices for how to relax. Since these require smaller energy transitions than releasing the energy all at 
once, they provide an easier pathway for relaxation - this is why the energy absorbed from the UV light 
is released as harmless (low energy) IR radiation. 

Slide 29: Organic Ingredients: Absorption Range 

Light absorption by molecules is similar to the emission of light by atoms with three key differences: 

• Light is captured instead of released. 

• Molecules absorb broader bands of wavelengths than atoms because there are multiple vibrational 
and rotational modes to which they can transition (for more details on molecular absorption concepts, 
see the Lesson 3 PPT and teacher notes). 

• There are multiple pathways for relaxation - the light emitted does not have to be the same wave- 
length as the light absorbed. 

Different molecules have different peak absorption wavelengths, different ranges of absorption and differ- 
ences in how quickly absorption drops off ("fat" curves as compared to "skinny" ones). It is important 
to realize that even within a molecule's absorption range, it does not absorb evenly and absorption at 
the ends of the range is usually low. For example, octyl methoxycinnamate has an absorption range of 
295 - 350 nm, but we would not expect it to be a strong absorber of light with a wavelength of 295 nm. 

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UV Absorption Demonstration: As one effort to prevent the circulation of counterfeit currency, bills 
are often printed with special chemicals that absorb specific wavelengths of UV light (this occurs because 
the energy of these UV rays matches the difference between the molecule's energy levels). When one of 
these bills is held under a UV light, these molecules absorb the UV light and reemit purple light in the 
visible spectrum that we can see (note that that the remitted light is not UV light which is not visible 
to the human eye). You can demonstrate this effect for your students by turning off the classroom lights 
and shining a UV light on different kinds of bills and watching the printed designs appear (these must be 
relatively recently printed; Euros and Canadian bills have particularly interesting designs). If you have two 
UV lights of different wavelengths, you may even be able to see two different designs due to the selective 
absorption of the different molecules used in the printing. 

Slide 30: Organic Ingredients: Absorbing UVA / UVB 

Many organic ingredients block "shortwave" UVA light (also called UVA 2 light and ranging from ~ 320 
to 340 nm) but not "longwave" UVA light (also called UVA 1 light and ranging from ~ 340 to 400 nm). 
Up till 2006, avobenzone was the only organic ingredient currently approved by the FDA that is a good 
blocker of longwave UVA light. 

This is a good point to give you students the Summary of FDA Approved Sunscreen Ingredients: Student 
Handout. Have students look at the different kind of molecules and compounds and see what kind of 
wavelengths are protected against by which ingredient. 

Slide 31: How are inorganic sunscreen ingredients different from organic ones? How might 
this affect the way they block UV light? (Question Slide) 

Have your students brainstorm how inorganic sunscreens might be different from organic ones and how 
this might affect the way they block UV light. 

Slide 32: Inorganic Ingredients: The Basics 

Inorganic compounds are described by a formula unit instead of a molecular formula. The big difference 
is that while a molecular formula tells you exactly how many of each kind of atom are bonded together 
in a molecule; the formula unit only tells you the ratio between the atoms. Thus while all molecules of 
an organic substance will have exactly the same number of atoms involved (and thus be the same size), 
inorganic clusters can be of any size as long as they have the correct ratio between atoms. This occurs 
because inorganic substances are held together by ionic, not covalent bonds. 

You may want to review some of the basics of bonding in inorganic compounds (electrostatic attraction 
between ions) as opposed to bonding in organic molecules (electron sharing via covalent bonds) with your 
students here. 

Slide 33: Inorganic Ingredients: Cluster Size 

Note: the proper scientific name for TiOi is "titanium (IV) oxide", but the older name "titanium dioxide" 
is more commonly used. 

This slide is a re-emphasizes the difference between a molecular formula and the formula unit of an inorganic 
substance. While the molecular formula indicates the actual number of atoms that combine together to 
form a molecule, the formula unit indicates the ratio of atoms that combine together to form an inorganic 
compound. Molecules are always the same size whereas inorganic compounds can vary in the number of 
atoms involved and thus the size of the cluster. 

Common Confusion: Inorganic compound clusters are often referred to informally as "particles". Stu- 
dents often confuse this use of the word particle with the reference to the sub-atomic particles (proton, 
electrons and neutrons) or with reference to a molecule being an example of a particle. 

Slide 34: Inorganic Ingredients: UV Blocking 

When an inorganic compound absorbs light, energy is converted from an electromagnetic form to a me- 

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chanical one (kinetic energy of electrons). The excited electrons use this kinetic energy to "escape" the 
attraction of the positively charged nuclei and roam more freely around the cluster. 

Because there are so many more atoms involved in an inorganic compound than in a molecule, there are 
also many more different energy values that electrons can have (students can think of these loosely as how 
"free" the electrons are to move about the cluster; how far from their original position they can roam). 
The greater number of possible energy states means that a greater range of wavelengths of UV light can 
be absorbed leading to the broader absorption spectrum shown in the graph. 

Slide 35: If inorganic sunscreens ingredients block UVA light so well, why doesn't everybody 
use them? (Question Slide) 

Have your students brainstorm reasons why sunscreen manufacturers and consumers might not want to 
use inorganic sunscreen ingredients. 

Slide 36: Appearance Matters 

One of the major reasons that people have not used inorganic ingredients in the past is because of their 
appearance. Before we knew how dangerous UVA rays were, sunscreens with organic ingredients seemed 
to be doing a good job (since they do block UVB rays). 

Applying too little sunscreen is very dangerous because this reduces a sunscreen's blocking ability while 
still giving you the impression that you are protected. In this situation people are more likely to stay out 
in the sun longer and then get burned. 

Slide 37: Why Do They Appear White? I 

Scattering is a physical process that depends on cluster size, the index of refraction of the cluster substance 
and the index of refraction of the suspension medium. No energy transformations occur during scattering 
(like they do in absorption); energy is simply redirected in multiple directions. The wavelengths (and 
energy) of light coming in and going out are always the same. 

Maximum scattering occurs when the wavelength is twice as large as the cluster size. Since traditional 
inorganic sunscreen ingredients have diameter > 200 nm, they scatter light which is > 400 nm in diameter 
- this is in the visible spectrum. 

Slide 38: Why Do They Appear White? II 

Multiple scattering is a phenomenon of colloids (suspended clusters). When light is scattered, at the micro 
level it goes in many directions. At the macro level, it eventually either goes back the way it came or 
forwards in the same general direction it was moving. These are known as back- and front- scattering and 
they contribute to reflection and transmission respectively. 

Note that the formula presented earlier (Reflection + Transmission + Absorption = 100%) still holds. 
Scattering simply contributes to the "reflection" and "transmission" parts of the equation. (For more 
details on scattering concepts, see the Lesson 4 PPT and teacher notes). 

Slide 39: Why Do They Appear White? Ill 

The scattering of visible light by ZnO and T1O2 is the cause of the thick white color seen in older sunscreens. 
When the different colors of visible light are scattered up and away by the sunscreen, they reach our eyes. 
Since the combination of the visible spectrum appears white to our eyes, the sunscreen appears white. 

Depending on your students' backgrounds, you may want to review how white light is a combination of all 
colors of light. 

You may also want to discuss how the pigment in our skin selectively absorbs some colors (wavelengths) of 
visible light, while reflecting others. This is what usually gives our skin its characteristics color. Different 
pigments (molecules) absorb different wavelengths; this is why different people have different color skin. 

Slide 40: Why don't organic sunscreen ingredients scatter visible light? (Question Slide) 

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Have your students brainstorm reasons why organic sunscreen ingredients don't scatter visible light. 

Slide 41: Organic Sunscreen Molecules are Too Small to Scatter Visible Light 

Traditional inorganic clusters are usually 200 nm or larger, causing scattering in the visible range (400 - 
700 nm). Organic sunscreen molecules are smaller than 10 nm (usually 1-20 Angstroms) and thus do not 
scatter in the visible range. 

You may want to talk about how while the individual organic sunscreen molecules are very small compared 
to inorganic sunscreen clusters (many formula units ionically bonded together creating a large cluster) and 
the wavelengths of visible light, they are big compared to many of the simple molecules that students are 
used to studying, such as water or hydrochloric acid. 

How big or small something seems is relative to what you are comparing it to. In this case, we are 
comparing sunscreen ingredients with the size of the wavelength of light. 

Slide 42: What could we do to inorganic clusters to prevent them from scattering visible 
light? (Question Slide) 

Have your students brainstorm what we could do to inorganic clusters to prevent them from scattering 
light. If students say "make them smaller", ask them how small the clusters would need to be in order to 
not scatter visible light. 

Slide 43: Nanosized Inorganic Clusters I 

When visible light is not scattered by the clusters, it passes through the sunscreen and is reflected by our 
skin (blue and green rays are absorbed by pigments in the skin and the red, yellow and orange rays are 
reflected to our eyes giving skin its characteristic color). 

Optional Animation: If you have time, you may want to demo the sunscreen animations for your class 
at this point. The animations are available at http://nanosense.org/activities/clearsunscreen/ 
index.html and are explained in the Sunscreens & Sunlight Animations: Teacher Instructions & Answer 
Key in Lesson 4. 

Slide 44: Nanosized Inorganic Clusters II 

As the graph shows, 200 nm clusters scatter significant portions of the visible spectrum, while 100 nm 
clusters do not. 

Changing the size of the cluster does not affect absorption since this depends on the energy levels in the 
substance which are primarily determined by the substance's chemical identity. 

Discussion Question for Students: Is it good or necessary to block visible light from reaching our skin? 

Answer: Visible light has less energy than UVA light and is not currently thought to do any harm to our 
skin thus there is no need to block it. Think about human vision: visible light directly enters our eyes on 
a regular basis without causing any harm. 

Slide 45: Nano-Sunscreen Appears Clear 

This slide shows the difference in appearance between traditional inorganic and nanosunscreens. 

Slide 46: In Summary I 

If you have not yet given your students the Overview of Sunscreen Ingredients: Student Handout, do so 
now. Use the handout to review the similarities and differences between the three kinds of ingredients. 

Key Similarities &: Differences: 

• Both kinds of inorganic ingredients have the same atoms, structure and UV absorption 

• Nano-inorganic clusters are much smaller than the cluster size of traditional inorganic ingredients, 
thus do not scatter visible light, thus are clear. 

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Slide 47: In Summary II 

The big benefit of nano-sunscreen ingredients is that they combine UVA blocking power with an acceptable 
appearance. 



Image Sources 



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www.ckl2.org 370 



Chapter 3 



Fine Filters- Teacher Materials 



3.1 Filtering Solutions for Clean Water 

Unit Overview 

Contents 

For Anyone Planning to Teach Nanoscience...Read This First! 
Fine Filters Overview, Learning Goals & Standards 
Unit at a Glance: Suggested Sequencing of Activities 
Alignment of Unit Activities with Learning Goals 
Alignment of Unit Activities with Curriculum Topics 
(Optional) Fine Filters Pretest/Posttest: Teacher Answer Sheet 

For Anyone Planning to Teach Nanoscience... Read This First! 

Nanoscience Denned 

Nanoscience is the name given to the wide range of interdisciplinary science that is exploring the special 
phenomena that occur when objects are of a size between 1 and 100 nanometers (10~ 9 m) in at least 
one dimension. This work is on the cutting edge of scientific research and is expanding the limits of our 
collective scientific knowledge. 

Nanoscience is "Science-in-the-Making" 

Introducing students to nanoscience is an exciting opportunity to help them experience science in the mak- 
ing and deepen their understanding of the nature of science. Teaching nanoscience provides opportunities 
for teachers to: 

• Model the process scientists use when confronted with new phenomena 

• Address the use of models and concepts as scientific tools for describing and predicting chemical 
behavior 

• Involve students in exploring the nature of knowing: how we know what we know, the process of 
generating scientific explanations, and its inherent limitations 

• Engage and value our student knowledge beyond the area of chemistry, creating interdisciplinary 
connections 

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One of the keys to helping students experience science in action as an empowering and energizing experience 
and not an exercise in frustration is to take what may seem like challenges of teaching nanoscience and turn 
them into constructive opportunities to model the scientific process. We can also create an active student- 
teacher learning community to model the important process of working collaboratively in an emerging area 
of science. 

This document outlines some of the challenges you may face as a teacher of nanoscience and describes 
strategies for turning these challenges into opportunities to help students learn about and experience 
science in action. The final page is a summary chart for quick reference. 

Challenges &: Opportunities 

1. You will not be able to know all the answers to student (and possibly your own) questions 
ahead of time ... 

Nanoscience is new to all of us as science teachers. We can (and definitely should) prepare ahead of time 
using the resources provided in this curriculum as well as any others we can find on our own. However, it 
would be an impossible task to expect any of us to become experts in a new area in such a short period of 
time or to anticipate and prepare for all of the questions that students will ask. 

... This provides an opportunity to model the process scientists use when confronted with 
new phenomena. 

Since there is no way for us to become all-knowing experts in this new area, our role is analogous to the 
"lead explorer" in a team working to understand a very new area of science. This means that it is okay 
(and necessary) to acknowledge that we don't have all the answers. We can then embrace this situation 
to help all of our students get involved in generating and researching their own questions. This is a very 
important part of the scientific process that needs to occur before anyone steps foot in a lab. Each time 
we teach nanoscience, we will know more, feel more comfortable with the process for investigating what 
we don't know, and find that there is always more to learn. 

One strategy that we can use in the classroom is to create a dedicated space for collecting questions. This 
can be a space on the board, on butcher paper on the wall, a question "box" or even an online space if 
we are so inclined. When students have questions, or questions arise during class, we can add them to the 
list. Students can be invited to choose questions to research and share with the group, we can research 
some questions ourselves, and the class can even try to contact a nanoscientist to help us address some of 
the questions. This can help students learn that conducting a literature review to find out what is already 
known is an important part of the scientific process. 

2. Traditional chemistry and physics concepts may not be applicable at the nanoscale level 

One way in which both students and teachers try to deal with phenomena we don't understand is to go 
back to basic principles and use them to try to figure out what is going on. This is a great strategy as long 
as we are using principles and concepts that are appropriate for the given situation. 

However, an exciting but challenging aspect of nanoscience is that matter acts differently when the particles 
are nanosized. This means that many of the macro-level chemistry and physics concepts that we are used 
to using (and upon which our instincts are based) may not apply. For example, students often want to 
apply principles of classical physics to describe the motion of nanosized objects, but at this level, we know 
that quantum mechanical descriptions are needed. In other situations it may not even be clear if the 
macroscale-level explanations are or are not applicable. For example, scientists are still exploring whether 
the models used to describe friction at the macroscale are useful in predicting behavior at the nanoscale 
(Luan & Robbins, 2005). 

Because students don't have an extensive set of conceptual frameworks to draw from to explain nanophe- 
nomena, there is a tendency to rely on the set of concepts and models that they do have. Therefore, there 

www.ckl2.org 372 



is a potential for students to incorrectly apply macroscale-level understandings at the nanoscale level and 
thus inadvertently develop misconceptions. 

... This provides an opportunity to explicitly address the use of models and concepts as 
scientific tools for describing and predicting chemical behavior. 

Very often, concepts and models use a set of assumptions to simplify their descriptions. Before applying 
any macroscale-level concept at the nanoscale level, we should have the students identify the assumptions 
it is based on and the situations that it aims to describe. For example, when students learn that quantum 
dots fluoresce different colors based on their size, they often want to explain this using their knowledge 
of atomic emission. However, the standard model of atomic emission is based on the assumption that the 
atoms are in a gaseous form and thus so far apart that we can think about their energy levels independently. 
Since quantum dots are very small crystalline solids, we have to use different models that think about the 
energy levels of the atoms together as a group. 

By helping students to examine the assumptions a model makes and the conditions under which it can be 
applied, we not only help students avoid incorrect application of concepts, but also guide them to become 
aware of the advantages and limitations of conceptual models in science. In addition, as we encounter 
new concepts at the nanoscale level, we can model the way in which scientists are constantly confronted 
with new data and need to adjust (or discard) their previous understanding to accommodate the new 
information. Scientists are lifelong learners and guiding students as they experience this process can help 
them see that it is an integral and necessary part of doing science. 

3. Some questions may go beyond the boundary of our current understanding as a scientific 
community... 

Traditional chemistry curricula primarily deal with phenomena that we have studied for many years and 
are relatively well understood by the scientific community. Even when a student has a particularly deep or 
difficult question, if we dig enough we can usually find ways to explain an answer using existing concepts. 
This is not so with nanoscience! Many questions involving nanoscience do not yet have commonly agreed 
upon answers because scientists are still in the process of developing conceptual systems and theories to 
explain these phenomena. For example, we have not yet reached a consensus on the level of health risk 
associated with applying powders of nanoparticles to human skin or using nanotubes as carriers to deliver 
drugs to different parts of the human body. 

... This provides an opportunity to involve students in exploring the nature of knowing: how 
we know what we know, the process of generating scientific explanations, and its inherent 
limitations. 

While this may make students uncomfortable, not knowing a scientific answer to why something happens 
or how something works is a great opportunity to help them see science as a living and evolving field. 
Highlighting the uncertainties of scientific information can also be a great opportunity to engage students 
in a discussion of how scientific knowledge is generated. The ensuing discussion can be a chance to talk 
about science in action and the limitations on scientific research. Some examples that we can use to begin 
this discussion are: Why do we not fully understand this phenomenon? What (if any) tools limit our ability 
to investigate it? Is the phenomenon currently under study? Why or why not? Do different scientists have 
different explanations for the same phenomena? If so, how do they compare? 

4. Nanoscience is a multidisciplinary field and draws on areas outside of chemistry, such as 
biology, physics, and computer science... 

Because of its multidisciplinary nature, nanoscience can require us to draw on knowledge in potentially 
unfamiliar academic fields. One day we may be dealing with nanomembranes and drug delivery systems, 
and the next day we may be talking about nanocomputing and semiconductors. At least some of the many 
areas that intersect with nanoscience are bound to be outside our areas of training and expertise. 

373 www.ckl2.org 



... This provides an opportunity to engage and value our student knowledge beyond the 
traditional areas of chemistry. 

While we may not have taken a biology or physics class in many years, chances are that at least some of 
our students have. We can acknowledge students' interest and expertise in these areas and take advantage 
of their knowledge. For example, ask a student with a strong interest in biology to connect drug delivery 
mechanisms to their knowledge about cell regulatory processes. In this way, we share the responsibility for 
learning and emphasize the value of collaborative investigation. Furthermore, this helps engage students 
whose primary area of interest isn't chemistry and gives them a chance to contribute to the class discussion. 
It also helps all students begin to integrate their knowledge from the different scientific disciplines and 
presents wonderful opportunities for them to see the how the different disciplines interact to explain real 
world phenomena. 

Final Words 

Nanoscience provides an exciting and challenging opportunity to engage our students in cutting edge science 
and help them see the dynamic and evolving nature of scientific knowledge. By embracing these challenges 
and using them to engage students in meaningful discussions about science in the making and how we 
know what we know, we are helping our students not only in their study of nanoscience, but in developing 
a more sophisticated understanding of the scientific process. 

References 

• Luan, B., & Robbins, M. (2005, June). The breakdown of continuum models for mechanical contacts. 
Nature 435, 929-932. 

Table 3.1: Challenges of teaching nanoscience and strategies for turning these challenges into 
learning opportunities. 



THE CHALLENGE... 



PROVIDES THE OPPORTUNITY TO... 



1. You will not be able to know all the answers to 
student (and possibly your own) questions ahead 
of time 



Model the process scientists use when confronted 

with new phenomena: 

Identify and isolate questions to answer 

Work collectively to search for information using 

available resources (textbooks, scientific journals, 

online resources, scientist interviews) 

Incorporate new information and revise previous 

understanding as necessary 

Generate further questions for investigation 



2. Traditional chemistry and physics concepts may 
not be applicable at the nanoscale level 



Address the use of models and concepts as scien- 
tific tools for describing and predicting chemical 
behavior: 

Identify simplifying assumptions of the model and 
situations for intended use 

Discuss the advantages and limitations of using 
conceptual models in science 

Integrate new concepts with previous understand- 
ings 



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374 



Table 3.1: (continued) 



THE CHALLENGE... PROVIDES THE OPPORTUNITY TO... 

3. Some questions may go beyond the boundary of Involve students in exploring the nature of know- 
our current understanding as a scientific commu- ing: 

nity How we know what we know 

The limitations and uncertainties of scientific ex- 
planation 

How science generates new information 
How we use new information to change our under- 
standings 

4. Nanoscience is a multidisciplinary field and Engage and value our student knowledge beyond 
draws on areas outside of chemistry, such as bi- the area of chemistry: 

ology and physics Help students create new connections to their ex- 

isting knowledge from other disciplines 
Highlight the relationship of different kinds of in- 
dividual contributions to our collective knowledge 
about science 

Explore how different disciplines interact to explain 
real world phenomena 



Fine Filters: Overview, Learning Goals & Standards 

Type of Courses: Chemistry 

Grade Levels: 9-12 

Topic Area: Separation of solutions 

Key Words: Nanoscience, nanotechnology, separation of mixtures, filtration, nanofiltration, solutions, 
water 

Time Frame: 4 class periods (assuming 50 - minutes classes), with extensions available 

Overview 

The shortage of clean drinking water is a pressing global issue. In the twentieth century, demand for 
water increased six fold, more than double the rate of growth of the human population. At the same time, 
pollution and over-extraction of water in many regions of the world has reduced the ability of supplies to 
meet the demand. The United Nations estimates that over a billion people lack access to safe drinking 
water. 

Part of the solution to the water crisis comes from filtration technologies that make water clean enough 
to drink. For water that contains salt, (97% of earth's water), reverse osmosis is now in use for removing 
sodium ions. Reverse osmosis is an expensive process, because it requires high pressure — and hence more 
energy in the form of electricity — to force the affluent (impure water) through the filter membrane. 

For water that does not contain salt, a new and more cost-effective technology — nanofiltration — is just 
beginning to be used. Nanofiltration can remove minerals, sugars, and color from water, and costs much 
less than reverse osmosis because the process requires much less pressure. There are a multitude of research 
efforts to develop nanomembranes for water filtration. Researchers anticipate that several forms of this 
new technology will be available in the next few years. This new generation of membranes is designed to 

375 www.ckl2.org 



be equally effective as currently used purification treatments, but significantly less expensive so that poor 
communities can afford clean drinking water. 

Enduring Understandings (EU) 

What enduring understandings are desired? Students will understand: 

1. A shortage of clean drinking water is one of the most pressing global issues. 

2. As a result of water's bent shape and polarity, water has unique properties, such as an ability to 
dissolve most substances. These properties are responsible for many important characteristics of 
nature. 

3. Pollutants can be separated from water using a variety of filtration methods. The smaller the particle 
that is to be separated from a solution, the smaller the required pore size of the filter and the higher 
the cost of the process. 

4. Innovations using nanotechnology to create a new generation of membranes for water filtration are 
designed to solve some critical problems in a cost-effective way that allows for widespread use. 

Essential Questions (EQ) 

What essential questions will guide this unit and focus teaching and learning? 

1. Why are water's unique properties so important for life as we know it? 

2. How do we make water safe to drink? 

3. How can nanotechnology help provide unique solutions to the water shortage? 

4. Can we solve our global water shortage problems? Why or why not? 

Key Knowledge and Skills (KKS) 

What key knowledge and skills will students acquire as a result of this unit? Students will be able to: 

1. Describe the global distribution of clean drinking water and explain some of the causes and conse- 
quences of water scarcity. 

2. Describe different types of filtration in terms of the pore size of the filter, substances it can separate, 
and cost of use. 

3. Use laboratory procedures to compare the relative effectiveness of different filtration methods on 
particle separation. 

4. Describe the basic structure and charge distribution of water. 

5. Explain how hydrogen bonding accounts for many of water's unique properties. 

Prerequisite Knowledge 

This unit assumes that students are familiar with the following concepts or topics: 

1. Atoms, molecules, ions. 

2. Homogeneous and heterogeneous solutions. 

3. Solute-solvent interaction between ionic and molecular solutes and water. 

NSES Content Standards Addressed 

K-12 Unifying Concepts and Process Standard 

As a result of activities in grades, K-12, all students should develop understanding and abilities aligned 
with the following concepts and processes: (1 of the 5 categories apply) 

www.ckl2.org 376 



• Form and function 

Grades 9-12 Content Standard A: Scientific Inquiry 

Abilities Necessary to Do Scientific Inquiry 

• Design and conduct scientific investigations. Designing and conducting a scientific investiga- 
tion requires introduction to the major concepts in the area being investigated, proper equipment, 
safety precautions, assistance with methodological problems, recommendations for use of technolo- 
gies, clarification of ideas that guide the inquiry, and scientific knowledge obtained from sources 
other than the actual investigation. The investigation may also require student clarification of the 
question, method, controls, and variables; student organization and display of data; student revision 
of methods and explanations; and a public presentation of the results with a critical response from 
peers. Regardless of the scientific investigation performed, students must use evidence, apply logic, 
and construct an argument for their proposed explanations. (12ASI1.2) 

• Formulate scientific explanations and models. Student inquiries should culminate in formu- 
lating an explanation or model. Models should be physical, conceptual, and mathematical. In the 
process of answering the questions, the students should engage in discussions and arguments that 
result in the revision of their explanations. These discussions should be based on scientific knowledge, 
the use of logic, and evidence from their investigation. (12ASI1.4) 

• Communicate and defend a scientific argument. Students in school science programs should 
develop the abilities associated with accurate and effective communication. These include writing and 
following procedures, expressing concepts, reviewing information, summarizing data, using language 
appropriately, developing diagrams and charts, explaining statistical analysis, speaking clearly and 
logically, constructing a reasoned argument, and responding appropriately to critical comments. 
(12ASI1.6) 

Grades 9-12 Content Standard B: Physical Science 

Structure and Properties of Matter 

Compounds. The physical properties of compounds reflect the nature of the interactions among its 
molecules. These interactions are determined by the structure of the molecule, including the constituent 
atoms and the distances and angles between them. (12BPS2.4) 

Grades 9-12 Content Standard E: Science and Technology 

Abilities of Technological Design 

• Propose designs and choose between alternative solutions. Students should demonstrate 
thoughtful planning for a piece of technology or technique. Students should be introduced to the 
roles of models and simulations in these processes. (12EST1.2) 

• Communicate the problem, process, and solution. Students should present their results to stu- 
dents, teachers, and other in a variety of ways, such as orally, in writing, and in other forms — including 
models, diagrams, and demonstrations. (12EST1.5) 

Grades 9-12 Content Standard F: Science in Personal and Social Perspectives 

Personal and Community Health 

• Selection of foods and eating patterns determine nutritional balance. Nutritional bal- 
ance has a direct effect on growth and development and personal well-being. Personal and so- 
cial factors — such as habits, family income, ethnic-heritage, body-size, advertising, and peer pres- 
sure — influence nutritional choices. (12FSPSP1.5) 

377 www.ckl2.org 



Population Growth 

• Populations can reach limits to growth. Carrying capacity is the maximum number of individu- 
als that can be supported in a given environment. The limitation is not the availability of space, but 
the number of people in relation to resources and the capacity of earth systems to support human 
beings. Changes in technology can cause significant changes, either positive or negative, in carrying 
capacity. (12FSPSP2.1) 

Natural Resources 

• Human populations use resources in the environment in order to maintain and improve 
their existence. Natural resources have been and will continue to be used to maintain human 
populations. (12FSPSP3.1) 

• The earth does not have infinite resources; increasing human consumption places severe stress 
on the natural processes that renew some resources, and it depletes those resources that cannot be 
renewed. (12FSPSP3.2) 

Environmental Quality 

• Many factors influence environmental quality. Factors that students might investigate include 
population growth, resource use, population distribution, overconsumption, the capacity of technol- 
ogy to solve problems, poverty, the role of economic, political, and religious views, and different ways 
humans view the earth. (12FSPSP4.3) 

Science and Technology in Local, National, and Global Challenges 

• Science and technology are essential social enterprises, but alone they can only indicate 
what can happen, not what should happen. The latter involves human decisions about the use of 
knowledge. (12FSPSP6.1) 

• Understanding basic concepts and principles of science and technology should precede 
active debate about the economics, policies, politics, and ethics of various science- and technology- 
related challenges. However, understanding science alone will not resolve local, national, or global 
challenges. (12FSPSP6.2) 

Unit at a Glance: Suggested Sequencing of Activities 

Overview 

The Fine Filters Unit has been designed in a modular fashion to allow you maximum flexibility in adapting 
it to your student's needs. Lesson 1 provides an introduction to the context and human need for clean 
drinking water. Combined with Lesson 3 (Nanofiltration), they make up the basic sequence for the unit. 
Lesson 2 is an extension that reviews some of the science basics of water. In particular, it reviews the 
structure of water and its unique properties based on the quantum mechanical model of the atom, the 
shape of the water molecule and the distribution of charge. 

Table 3.2: 

Lesson Basic Sequence Optional Extensions 

Lesson 1: The Water Crisis V 

Lesso 

W3VW.C 



Lesson_,2: The Science of Water » V 

avw.cklz.org ni , O I O 

Lesson 3: Nanonltration y 



Most lessons contain an interactive presentation and one or more options for activities so you can tailor the 
depth and duration of the lesson to meet your needs. The following pages contain a suggested sequencing 
of activities for the unit, but of course there are other combinations possible. 

Suggested Sequencing of Activities for Unit 

Table 3.3: 



Lesson 



Teaching Days Main Ac- Learning Goals Assessment 

tivities and 
Materials 



Homework 



Lesson 1: 


2 days: Day 1 


The Water 


EU:1 


Initial Ideas 


Student Data 






Crisis: Pow- 


KKS:1 


Worksheet 


Worksheet 






erPoint and 












Discussion 












Initial Ideas: 












Student Work- 












sheet 










Day 2 (10 min 


Take and re- 




Water Crisis 






only for quiz) 


view quiz 




Quiz 




Lesson 2: 


3 days: Day 1 


Science of Wa- 


EU: 2 




Read Sci- 


The Science of 




ter PowerPoint 


KKS: 3, 4 




ence of Water 


Water 




and Discussion 






Lab Activity 
and generate 
hypotheses 


(Optional) 


Day 2 


Science of Wa- 




Reflection 


Reflection 






ter Lab Activi- 




on Guiding 


on Guiding 






ties 




Questions 


Questions 




Day 3 (35 min) 


Reflection on 
Guiding Ques- 
tions Take and 
review quiz 




Science of Wa- 
ter Quiz 




Lesson 3: 


3 days: Day 1 


Nanofiltration: 


EU:3,4 


Which Method 


Nanofiltration: 


Nanofiltration: 




PowerPoint 


KKS:2,3 


is Best Work- 


Student Read- 






and Discussion 




sheet 


ing 






Which Method 






Read Fil- 






is Best Activity 






tration Lab 
and generate 
hypotheses 




Day 2 


Comparing 




Filtration Lab 


New Nano- 






Nanofilters to 




Activity Work- 


Membranes 






Conventional 




sheet 


Student Read- 






Filters Lab 






ing 



Activity 



379 



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Table 3.3: (continued) 



Lesson 



Teaching Days Main Ac- Learning Goals Assessment 

tivities and 
Materials 



Homework 



Day 3 



Cleaning 

Jarny's Water 

Discuss Nano- 

Membranes 

Reading 

Discussion 

of Reflection 

on Guiding 

Questions 



Jarny Student 
Report 

Final Reflec- 
tions 



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380 



Table 3.4: 



What enduring understand- 
ings (EU) are desired? Stu- 
dents will understand: 



What essential questions What key knowledge and 

(EQ) will guide this unit and skills (KKS) will students ac- 
focus teaching and learning? quire as a result of this unit? Stu- 

dents will be able to: 



1. A shortage of clean drink- 
ing water is one of the most 
pressing global issues. 

2. As a result of water's bent 
shape and polarity, water 
has unique properties, such 
as an ability to dissolve 
most substances. These 
properties are responsible 
for many important charac- 
teristics of nature. 

3. Pollutants can be sepa- 
rated from water using a 
variety of filtration meth- 
ods. The smaller the parti- 
cle that is to be separated 
from a solution, the smaller 
the required pore size of 
the filter and the higher the 
cost of the process. 

4. Innovations using nan- 
otechnology to create a 
new generation of mem- 
branes for water filtration 
are designed to solve some 
critical problems in a cost 
effective way that allows 
for widespread use. 



1. Why are water's unique 
properties so important for 
life as we know it? 

2. How do we make water safe 
to drink? 

3. How can nanotechnology 
help provide unique solu- 
tions to the water short- 
age? 

4. Can we solve our global 
water shortage problems? 
Why or why not 



1. Describe the global distri- 
bution of clean drinking 
water and explain some 
of the causes and conse- 
quences of water scarcity. 

2. Describe different types of 
filtration in terms of the 
pore size of the filter, sub- 
stances it can separate, and 
cost of use. 

3. Use laboratory procedures 
to compare the relative ef- 
fectiveness of different fil- 
tration methods on particle 
separation. 

4. Describe the basic struc- 
ture and charge distribu- 
tion of water. 

5. Explain how hydrogen 
bonding accounts for 
many of water's unique 
properties. 



Alignment of Unit Activities with Learning Goals 



Table 3.5: 



Lesson 1 



Lesson 2 



Lesson 3 



Presentation 
Activity 



Introduction / Water Science of Water 

Crisis 

Student Reading, Data Water Lab Activity 

Worksheet 



Nano filtration 

Student Reading / 
Jarny / Filtration Lab 



381 



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Table 3.5: (continued) 



Lesson 1 



Lesson 2 



Lesson 3 



Assessment 

Learning Goals 
Students will under- 
stand... 

EU 1. A shortage of 
clean drinking water is 
one of the most pressing 
global issues 
EU 2. As a result of wa- 
ter's bent shape and po- 
larity, water has unique 
properties, such as an 
ability to dissolve most 
substances. These prop- 
erties are responsible for 
many important charac- 
teristics of nature. 
EU 3. Pollutants can 
be separated from wa- 
ter using a variety of fil- 
tration methods. The 
smaller the particle that 
is to be separated from a 
solution, the smaller the 
required pore size of the 
filter and the higher the 
cost of the process 
EU 4. Innovations us- 
ing nanotechnology to 
create a new genera- 
tion of membranes for 
water filtration are de- 
signed to solve some 
critical problems in a 
cost-effective way that 
allows for widespread 
use. 

Students will be able 
to... 

KKS1. Describe the 
global distribution of 
clean drinking water 
and explain some of 
the causes and con- 
sequences of water 
scarcity. 



Quiz/ Initial 
Worksheet 



Ideas Label Results/ Quiz 
Reflection Worksheet 



Lab Results / 3 amy, Re- 
flection Worksheets 



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382 



Table 3.5: (continued) 



Lesson 1 



Lesson 2 



Lesson 3 



KKS2. Describe differ- 
ent types of filtration in 
terms of the pore size of 
the filter, substances it 
can separate, and cost of 
use. 

KKS4. Use labora- 
tory procedures to com- 
pare the relative effec- 
tiveness of different fil- 
tration methods on par- 
ticle separation. 
KKS3. Describe the ba- 
sic structure and charge 
distribution of water. 
KKS5. Explain how 
hydrogen bonding ac- 
counts for many of wa- 
ter's unique properties. 



Alignment of Unit Activities with Curriculum Topics 



Table 3.6: Chemistry 



Unit Topic 



Chapter Topic 



Subtopic 



Fine Filters Specific Materi- 

Lessons als 



Structure of Mat- Electron Configu- Atomic Structure 



ter 



ration 



Lesson 2 
(L2): Sci- 
ence of 
Water 



Slides 



L2: 3-10 



Bonding 



Slides 



Lesson 
(L2): 

ence 

Water 



2 

Sci- 

of 



L2: 11-19 



383 



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Table 3.6: (continued) 



Unit Topic 


Chapter Topic 


Subtopic 


Fine ] 
Lessons 


Filters Specific 
als 


Materi- 


Chemical Equilib- 
rium 


Solutions 


Nature of solutions 
Precipitates 
Common Ion Ef- 
fect 


• Lesson 
(L2): 
ence 


Slides 

2 . L2: 

Sci - . L3: 
of 


(all) 
(all) 



Water 

Lesson 

3 (L3): 

Nanofiltra- 

tion 



Activity /Handout 



L2 



Science 
of Wa- 
ter 
Labs 



L3 



Reflecting 
on 

Guid- 
ing 
Ques- 
tions 



The 
Filtra- 
tion 
Spec- 
trum 
Which 
Method 
is Best? 

Cleaning 
J amy's 
Water 

Comparing 
Filtra- 
tion to 
Nanofil- 
tration 
Lab 
Activi- 
ties 



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384 



Table 3.7: Biology 



Unit Topic 



Chapter Topic 



Subtopic 



Fine Filters Specific Materials 

Lessons 



Nature of Life 



The Chemistry of The Nature of Fine Filters 



Slides 



Life 



Matter; Properties 
of Water; Carbon 
Compounds 



Lesson 2 

(L2): Sci- 
ence 
Water 



. L2: 20-32 
r Activity/Handout 

. L2 

— Science 
of Wa- 
ter 
Labs 

— Science 
of Wa- 
ter 
Quiz 



Table 3.8: Physics 



Unit Topic 



Chapter Topic 



Subtopic 



Fine Filters Specific Materi- 

Lessons als 



Light and Optics Light Rays 



Electron clouds 


Fine Filters 


Slides 


Orbitals Charges 


• Lesson 2 

(L2): The 
Science of 
Water 


. L2: 5-16 



385 



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Table 3.9: Environmental Science 



Unit Topic Chapter Topic Subtopic Fine Filters Specific Materials 

Lessons 

Water Our Water Re- Solutions to Water Slides 

sources Shortages 



Lesson 1 . L1: x _ 2 7 

(LI): The 

Water Crisis Activity/Handout 

. The World- 
Wide Water 
Shortage: 
Student 
Reading 

. The Water 
Crisis: Stu- 
dent Data 
Worksheet 

. The Water 
Crisis Initial 
Ideas 

• Student 
Quiz 



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Table 3.9: (continued) 



Unit Topic 



Chapter Topic 



Subtopic 



Fine Filters Specific Materials 

Lessons 



Freshwater Pollu- Wastewater Treat- 
tion ment Plants 



Slides 



Lesson 2 


• 


L2: 1-34 


(L2): The 






Science of 


Activity /Handout 


Water 






Lesson 


• 


L2: The Sci- 


3 (L3): 




ence of Wa- 


Nanofiltra- 




ter Quiz 


tion 


• 


L3: 

Comparini 
Filtra- 
tion 
and 

Nanofil- 
tration 
Lab 
Activi- 
ties 

Reflecting 
on the 
Guid- 
ing 
Ques- 
tions 



387 



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Table 3.9: (continued) 



Unit Topic 



Chapter Topic 



Subtopic 



Fine Filters Specific Materials 

Lessons 



Pathogens 



Lesson 

3 (L3): 

Nanofiltra- 

tion 



Slides 

. L3: 1-21 

Activity /Handout 

• Reading: 
New Nano- 
Membranes 

• Which 
Method is 
Best? 

• Jarny Water 
Activity 

• Comparing 
Filtration 
and Nanofil- 
tration Lab 
Activities 

• Reading: 
New Nano- 
Membranes 



Fine Filters Pretest/Posttest: Teacher Answer Sheet 

20 points total 

1. Which of the following types of contaminants can nanomembranes filter out of water? For which of 
these, would you typically use a nanomembrane for removal? Explain why or why not. (1 point each, total 
of 12 points) 

Table 3.10: 



Can a nanomembrane filter it out? 



Is a nanomembrane the best way to filter it out? 



Bacteria Yes or No Yes or No 



Lead (Pb 2+ ) Yes or No Yes or No 



Why /why not: Bacteria are large enough that mi- 
cromembranes can also filter them out of water. 
Micromembranes are less expensive to use and the 
large bacteria would quickly foul the nanomem- 
brane. 

Why /why not: Divalent ions (such as lead) are 
too small to be separated out by micro- or ultra- 
filtration. Nanofiltration can remove them from 
water and is less expense than reverse osmosis 
(which would also remove them). 



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388 



Table 3.10: (continued) 



Can a nanomembrane filter it out? 



Is a nanomembrane the best way to filter it out? 



Salt (Na + and CI") Yes or No Yes or No 



Sand Yes or No Yes or No 



Why /why not: Monovalent ions are too small to be 
filtered out by current nanomembranes. Reverse 
osmosis must be used. 

Why/why not: Sand is large enough that it can 
be filtered by a simple mesh cloth. This is less 
expensive to use and the sand would quickly foul 
the nanomembrane. 



2. Name two benefits that nanomembranes bring to the filtration of water that help to address the world's 
problem of a scarcity of clean drinking water. (1 point each, 2 points total) 

• More effective in removing particles of a given size 

• More cost efficient than other technologies to remove small particles 

• Nanofiltration can be engineered in many different ways (design flexibility) 

Common Incorrect Answer: 

• Can remove smaller particles than existing technologies (RO removes smaller particles) 

3. Describe three ways in which nanofilters can operate differently than traditional filters to purify water: 
(2 points each, 6 points total) 

• Layering: Nanomembranes can be uniquely designed in layers. This allows different parts of the 
membrane (the different layers) to be made out of different materials and have different properties 
to target different contaminants. 

• Embedded Agents: Can embed specialized substances that do specific jobs in relation to certain kinds 
of contaminants - for example a chemical that kills bacteria on contact 

• Water Channels: Create hydrophilic tubes in membranes that "pull" water through while keeping 
everything else out 

• Electrostatic Repulsion 1: You can weave into the membrane a type of molecule than can conduct 
electricity and repel oppositely charged particles, but let water through. 

• Electrostatic Repulsion 2: Pores of one to two nanometers in diameter create an electric field over 
the opening. This electric field is negative and repels negatively charged particles dissolved in water 

• Self- Cleaning: Can send signal for them to self-clean (remove fouling residue) 

• Less pressure is needed than conventional RO filters 

The Water Crisis 

Contents 



Introduction to the Water Crisis: Teacher Lesson Plan 

The Water Crisis: PowerPoint Slides with Teacher Notes 

The Water Crisis Student Data Worksheet: Teacher Instructions & Answer Key 

Fine Filters Initial Ideas: Teacher Instructions 

The Water Crisis: Quiz Answer Key 

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Introduction to the Water Crisis: Teacher Lesson Plan 

Orientation 

This lesson is an introduction to the context and human need for clean drinking water. Many students in 
the United States are unaware that in several parts of the world, clean drinking water is unavailable. This 
introductory lesson is intended to increase students' awareness of the problem in terms of human health 
and as a potential source of conflict between nations, especially as the world population grows. 

A key goal is to spark students' interest by addressing a topic of personal and global significance. It is 
within the context of the urgent need for clean water by the people of several nations that they will better 
understand the significance that nanomembrane filtration technology could potentially have on helping to 
solve one of the current largest global problems. They will refine this understanding over the course of the 
unit and have a chance to reflect on their initial thoughts at the end of the unit. 

• The Water Crisis PowerPoint slide set introduces facts about the global distribution of fresh water 
geologically. Areas of the world that do not have access to enough clean drinking water are high- 
lighted. Per capita water usage, wealth, and access to sanitation are shown for several countries, and 
consequences from drinking contaminated water are highlighted. The final slide in the set introduces 
the driving questions for the unit. 

• The Water Crisis: Student Data Worksheet captures the images of the data graphs and tables 
embedded in the slide set. The questions associated with the data sets that are designed to get 
students to think about the information portrayed. We recommend that the students do the data 
sheet as a homework assignment previous to seeing the slides. Alternately, they can complete it as 
you present the slides, pausing at each slide that portrays a data representation in order to give 
students time to think about the information depicted. 

• The Initial Ideas: Student Worksheet gives students the chance to draw on their existing knowledge 
to formulate first thoughts about the unit. This is a great tool for eliciting students' prior knowledge 
(and possible misconceptions) related to the unit topics. 

• The Water Crisis: Student Quiz can help you to assess the student understandings before the lesson 
is taught, so you can adjust the lesson appropriately, or it can be used as a summative evaluation 
after the lesson. 

Essential Questions (EQ) 

What essential questions will guide this unit and focus teaching and learning? 

(Numbers correspond to learning goals overview document.) 

2. How do we make water safe to drink? 

3. How can nanotechnology help provide unique solutions to the water shortage? 

4. Can we solve our global water shortage problems? Why or why not? 
Enduring Understandings (EU) 

Students will understand: 

(Numbers correspond to the learning goals overview document.) 

1. A shortage of clean drinking water is one of the most pressing global issues. 

Key Knowledge and Skills (KKS) 

Students will be able to: 

(Numbers correspond to the learning goals overview document.) 

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1 . Describe the global distribution of clean drinking water and explain some of the causes and consequences 
of water scarcity. 

Table 3.11: Introduction &: Initial Ideas Timeline 



Day 



Activity 



Time 



Materials 



Prior to this lesson 



Day 1 (50 min) 



Homework: Water Cri- 40 min 
sis: Student Data Work- 
sheet 

Hand out the Initial 10 min 
Ideas Student Work- 
sheet and have students 
work alone or in pairs to 
brainstorm answers to 
the driving questions. 
Let students know that 
at this point they are 
just brainstorming ideas 
and they are not ex- 
pected to be able to 
fully answer the ques- 
tions. 

Show the Water Crisis: 30 min 
PowerPoint Slides, us- 
ing the question slides 
and teacher's notes to 
start the class discus- 
sion. 



Photocopies of Water 

Crisis: Student Data 

Worksheet 

Copies of Fine Filters 

Initial Ideas: Student 

Worksheet 



Fine Filters Initial 
Ideas: Teacher Instruc- 
tions 



Water Crisis: Pow- 
erPoint Slides & 
Teacher Notes 

Computer and projec- 
tor 



Hand out the Water 
Crisis: Student Data 
Worksheet if students 
did not complete it as 
a homework assignment 
the night before. Stu- 
dents can interpret the 
data representations or 
update their responses 
as you show the Power- 
Point slide set. 



Water Crisis: Student 
Data Worksheet 



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Table 3.11: (continued) 



Day 



Activity 



Time 



Materials 



Day 2 (10 min) 



Return to whole class 10 min 
discussion and have stu- 
dents share their ideas 
with the class to make 
a "master list" of initial 
ideas. The goal is not 
only to have students 
get their ideas out in the 
open, but also to have 
them practice evaluat- 
ing how confident they 
are in their answers. 
This is also a good 
opportunity for you to 
identify any miscon- 
ceptions that students 
may have to address 
throughout the unit. 
Optional: Water Crisis: 7-10 min 
Student Quiz 



Photocopies of Water 
Crisis: Student Quiz 
Water Crisis: Quiz An- 
swer Key 



The Water Crisis 




A lack of clean water results in poverty, disease and death 

Question 

Have You Ever Gotten Sick from Drinking Impure Water? Do You Know Someone Who Has? 

Clean Water is Necessary for Life 



• Drinking 
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392 




Figure 3.1 




Figure 3.2 



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• Bathing 

• Agriculture 

• Sanitation 

World Water Gap 

• Despite the apparent abundance of clean water in the US and most of the developed world, more 
than 20% of the Earth's population lacks clean, safe drinking water. 




',' ' / 



Figure 3.3 
How is the World's Water Distributed? I 

• Less than 3% of Earth's water is fresh water 

• The vast majority (97%) is undrinkable salt water in the oceans 

How is Water Distributed? II 

• Of the fresh water, most is in ice caps and glaciers, and some is in ground water 

• Less than 1% is in more easily accessible surface water (lakes, swamps, rivers, etc.) 

How is Water Distributed? Ill 

• Most of the surface water is in lakes; a bit is in swamps and rivers 

• The point: very little water is easily available for drinking 

Water is Scarce in Some Regions 

• 2.4 billion people live in highly water-stressed areas 

No Single Cause for the Water Crisis 
Many factors 

• Climate and geography 

• Lack of water systems and infrastructure 

• Inadequate sanitation 

— 2.6 billion people (40% of the world's population) lack access to sanitation systems that separate 
sewage from drinking water 

— Inadequate sanitation and no access to clean water have been highly correlated with disease 

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waft* 3* 




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Figure 3.4 



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Figure 3.5 



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( iqufcd) 



Figure 3.6 




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Current Water Scarcity: 2006 



Figure 3.7 



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396 




Figure 3.8 



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Figure 3.9 



Pollution is a Big Problem Too 



Types of pollution in fresh water: 



Sewage is the most common 
Pesticides and fertilizers 
Industrial waste dumping 
High levels of arsenic and fluoride 



Water Scarcity is Projected to Worsen 

Question 

Why is the Water Shortage Projected to Worsen? 

World Population is Increasing 

Question 

In What Ways Would an Increasing World Population Affect Water Consumption? 

Where Clean Water Use is Rising 

Trends in Population and Water Use 

Question 

Is There a Relationship Between Poverty and a Lack of Clean Drinkable Water? 

Countries Differ Widely in Water Usage 

Countries Differ Widely in Wealth 

Notice Any Correlations? 

Many Without Access Live in Poverty 



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398 



1995 



Freshwater Stress 



2025 





Wstpr wthmwiH *s [wrrentoopof "f*»l aval table 

M Over 40% ■ 20% - 10% 

40% - 20% ■ Less than 1 0K 

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Figure 3.10 



World Population: 1950-2050 




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Source: U.S. Census Bureau. International Data Base. August 2006 version. 



Figure 3.11 



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Global Annual Water Withdrawal by Sector, 1900-2000 





5000 




4.500 


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1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 

Source: Abramovitz 1 996 ( 1 ) 



Figure 3.12 





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Source: U.S. OiwwBihh**. Mernafonal Dan Bat* I 



Global Annual Water Withdrawal by Sector 
1950-2000 



2 



3 




Source AbramovlU, tm 



1950 i960 1970 1980 1990 2000 
Year 



Figure 3.13 



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400 



Average Daily Water Use Per Person (1998-2002) 
For Selected Countries 



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Figure 3.14 



Average Wealth (Purchasing Power Per Person in 
2005) For Selected Countries 



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Average Dally Water User Per Person 
& Wealth For Selected Countries 



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sit m 



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Figure 3.17 



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402 



• People without clean water 

— Almost two in three people survive on less than $2 a day, with one in three living on less than 
$1 a day 

• People without sanitation 

— Of the 2.6 billion people who do not have adequate sanitation, a little more than half live on 
less than $2 a day 

Impact of Water Scarcity I 




Figure 3.18: National Geographic, "The World Water Gap" World Water Forum, The Hague March 17-22, 
2000 



• Health, education, and economic growth are impacted 

• World Water Forum estimates: 

— 1.4 billion people lack clean drinking water 

— 2.3 billion people lack adequate sanitation 

— 7 million people die yearly from diseases linked to water 

— Half the world's rivers and lakes are badly polluted 

— Shortages could create millions of refugees seeking homes in a location accessible to water 

Impact of Water Scarcity II 

• World Health Organization estimates: 
% of all sickness in the world is attributable to unsafe water and sanitation 



— The leading causes of death in children under 5 are related to unclean water; there are about 
5, 000 child deaths every day 

— Without action, as many as 135 million people could die from water-related diseases by 2020 

Impact of Water Scarcity III 



Carrying water takes time! 



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Figure 3.19 




Photographer: 
Chantal Boulanger 



Figure 3.20 



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404 



Women and children can trek miles every day to retrieve water 

This hard manual labor takes time that they might otherwise spend pursuing education or 

earning additional income 



Children Carrying Water 




Figure 3.21 

War for Diminishing Resources? 

"The next world war will be over water," says Vice President Ismail Serageldin from the World Bank 




Figure 3.22 



How Can We Address the Water Crisis? 



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• Use less water 

— More efficient irrigation, like drip irrigation 

— Low-flow shower and toilets 

— Use native plants for crops and landscaping 

— Eat less meat 

• Find new sources of clean water 

— Um... Where? On the moon? 

• Treat the undrinkable water that we have 

— Use reverse osmosis to desalinize salt (ocean) water 

— Clean polluted water using filters, chemicals, and UV light 

Using Filters to Clean Water 

• Pebbles, sand, & charcoal filter out large particles 

• Membranes filter out smaller particles 

• It is efficient to use a series of membranes to filter increasingly smaller particles 



Microfiltration Nanofi tration 

Ultrafiltration 



Reverse Osmosis 




g ' t coll « Virus** 

«*- Oil T Protons 

C MacromolteulM 

O Col Oil! S 

•J Suspended 
Partcies 



i Ions 
STiaii 
Compounds 



Can Nanotechnology Help? 



Figure 3.23 



Nanotechnology offers new solutions to filter small particles 

— Unique properties at the nanoscale mean that membranes can be made to filter by electrical 
and chemical properties 

— A huge effort to create better, cheaper nanomembrane filters isv currently underway! 



Questions 



How Do We Make Undrinkable Water Safe to Drink? 

How can Nanotechnology Help Provide Solutions to the Water Shortage? 

Can We Solve Our Global Water Shortage Problems? 



- Why or Why Not? 
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406 




Membranes 
clean water by 
filtering out 
unwanted 
substances 




Professor Eric 
Hoek at UCLA is 
patenting a new 
nanomembrane 
filter 



Figure 3.24 



Teacher Notes 

Overview 

This set of slides provides background information on the importance of clean water, why there is a problem 
with access to clean water, the geographical distribution of fresh water sources globally, a correlation 
between a country's wealth and water usage, and describes the impact of fresh water shortages on the 
human population. In this way we establish an important global context for learning about the potential 
of nanomembranes to help solve this problem of water shortage. These notes are intended to provide you 
with additional background content for each slide. Some slides will contain questions. These are invitations 
to engage students in an interactive classroom discussion about the question raised. You will also find a 
variety of resources for optional use to deepen your own knowledge or to engage students in an activity 
that relates to key points on the slide. 

Slide 1: Title Slide 

Slide 2: Have You Ever Gotten Sick from Drinking Impure Water? (Question Slide) 

Discuss with your students what their experiences have been (or that they have known about) when 
someone drinks impure water. This discussion is intended to draw on students' personal understanding of 
the negative effects of not drinking pure water, so as to better peak their interest in the topic. In the event 
that students have not had experiences or heard about them, they may have heard about Montezuma's 
revenge! 



Baytel Associates conducted a study to identify drinking water contaminants that cause health problems 
worldwide. They found so many different contaminants that they prioritized the list to include the twelve 
"if eliminated" that would have the greatest impact on public health. The twelve contaminants identified 
are: cholera, enteric bacteria, Rota- and polio viruses, intestinal protozoan, Ascaris (intestinal round- 
worm), Dracunculus medinensis (Guinea worm), Trichuris trichiura (whipworm), Enerobious vermicularis 
(pinworm), fluorides, heavy metals, nitrates, and synthetic chemicals. 

From the report "Critical Drinking Water Contaminants: A Global Perspective," as reported by US Water 



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News online, June 1995. See http://www.uswaternews.com/archives/arcquality/5drink.html 

Slide 3: Clean Water is Necessary for Life 

Clean water is needed for these four major areas. Sanitation refers to the ability to provide adequate 
sewage disposal that separates sewage waste from drinking water supplies. Disease in a community is 
highly correlated with a lack of public sanitation. 

Slide 4: World Water Gap 

This slide informs students that many people globally do not have access to clean drinking water. The 
"gap" is a term to describe the difference between the number of people who need clean drinking water 
compared with the number of people who need clean drinking water. Later we'll see a global map of fresh 
water distribution. 

Based on data from NASA, the World Health Organization, and other agencies, a report produced by the 
United Nations Environment Programme predicts: 

• Severe water shortages already affect at least 400 million people today and are projected to affect 
4 billion people by 2050. Southwestern states such as Arizona will face severe fresh water shortages 
by 2025. 

• Adequate sanitation facilities (bathrooms) are lacking for 2.4 billion people, about 40% of humankind. 

See http://www.usatoday.com/news/nation/2003-01-26-water-usat_x.htm 

Slide 5: How is the World's Water Distributed? I 

Slides 5, 6, and 7 show the distribution of water globally. Many students do not know that most of the 
world's water is salt water (undrinkable and/or unusable for agriculture). The green box shows a physical 
depiction of the amount of fresh water relative to salt water, globally. 

Why can't we use salt water to drink or for agriculture? 

Some students do not understand why we cannot drink salt water. Department of Energy's scientist, Prof 
Bill's, explanation of why we cannot drink salt water is brief and to the point: "Humans can't drink salt 
water because the kidneys can only make urine that is less salty than salt water. Therefore, to get rid of 
all the excess salt taken in by drinking salt water, you have to urinate more water than you drank, so you 
die of dehydration." 

Why can't salt water be used for agriculture? In general, too much salt will interfere with the chemistry 
in a plant that allows the plant to make food and to obtain energy from food. In addition, plants usually 
get their water through their root system by a process called osmosis (students who have had biology will 
know about this process). Osmosis involves the passage of water across the membrane of a cell from an 
area of greater concentration to an area of lesser concentration. If the plant is surrounded by salt water, 
the plant will tend to pass fresh water from their inside structures to the soil through the roots, causing 
the plant to lose, not absorb water. 

There is a type of plant, called halophytes, that have special structures that separate the salt in such a 
way that it is prevented from mingling with the rest of the plant, allowing the plant to survive in a salt 
water environment. 

Slide 6: How is Water Distributed? II 

This slide depicts the section in the green box representing the proportion of fresh global water, expanded 
to show where the 3% of fresh water may be found: 68.7% icecaps and glaciers, 30.1% ground water, and 
only 0.3% surface water. 

Slide 7: How is Water Distributed? Ill 

This slide depicts the distribution of the 0.3% surface water: 87% lakes, 11% swamps, and 2% rivers. 

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Slide 8: Water is Scarce in Some Regions 

This calculated approximation, that 2.4 billion people are living in highly water-stressed areas, comes from 
N.Utsumi, Thesis, The University of Tokyo (2006). 

Fresh water scarcity or stress is described in a variety of ways. 

This is a map from a global view showing the geographic distribution of fresh water, either as surface water 
or in underground aquifers, as it relates to the population's need for fresh water in that region. Depending 
on the area's population density and the climate's ability to renew these water supplies, a geographic area 
can be described by the percent of its available fresh water being used annually compared to how much 
fresh water is potentially available for use. The higher the percent of water being used compared to what 
is potentially available, the more scarce the fresh water supply. The total potentially available fresh water 
cannot be completely used. Water availability depends on the climate, the season, the amount of snowmelt, 
and the infrastructure to capture, store, clean, and deliver it. 

Water scarcity is often described in two ways: 

Physical water scarcity is a term used to describe an area whose primary water supply is developed at 
60% or greater than the total potential capacity. One must understand that the total potential capacity 
includes water that can never be entirely accessed. These countries do not have sufficient fresh water to 
meet their demands for agriculture, domestic water, industrial sectors, and environmental requirements. 
Food has to be imported or salt water must be treated by an expensive desalination process in order to 
get enough fresh water for agriculture. Agriculture consumes about 70% of fresh water supplies. 

Economic water scarcity is a term describing a region that has adequate physical water resources to 
meet their water supply needs, but must increase the availability of the water through additional storage 
and conveyance facilities. Most of these countries face severe financial and development capacity problems 
for increasing the primary water supply, by building the needed infrastructure. 

Water shortages are greatest in equatorial regions with increasing populations. 

Slide 11 will show freshwater stress simply as the water withdrawal as a percentage of the total available. 
These are associated with different percentages. 

From Science, August 25, 2006, published by AAAS: 

Water scarcity can be an index defined as Rws = (W - S)/Q where W, S, and Q are the annual water 
withdrawal by all the sectors, the water use from desalinated water, and the annual renewable fresh water 
resources (RFWR), respectively. 

Slide 9: No Single Cause for the Water Crisis 

This slide highlights the major causes for the water crisis. An arid climate does not produce much rainfall. 
Areas with sufficient rainfall and fresh water supply often lack systems to clean and deliver water to the 
people, especially in rural areas. It is estimated by the World Health Organization that 40% of the world's 
population lack sufficient sanitation systems to keep the potable (drinking) water separate from human 
wastes. 

Arsenic and fluoride are pollutants that leach out of rocks into the water in some areas. While small 
quantities of fluoride are good for teeth, larger quantities are bad. These must be removed before the 
water is considered to be safe for drinking. 

Slide 10: Pollution is a Big Problem Too 

The most common type of pollution is untreated sewage that mixes with the drinkable water supply. 
Sewage contains disease-causing bacteria. Secondly, agriculture contributes pesticides and fertilizer. The 
pesticides contain poisonous substances that dissolve in water and the fertilizer breaks down to release 
nitrates into the water. Industrial pollutants contribute heavy metals to the water supply in some areas. 

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All of these must be removed from water, according to clean water standards, for water to be safe to drink. 

Slide 11: Water Scarcity is Projected to Worsen 

This slide depicts the global distribution of fresh water in the year 1995 and the predicted water distribution 
in the year 2025. The colors represent the percentage of water withdrawn compared with the total amount 
of water available. The light orange represents mild water stress and the darker orange represents extreme 
water stress. The blue areas are considered to be free from freshwater stress. 

The graph in the lower right corner shows the amount of people, in billions, suffering from water stress 
and scarcity, in 1995, then as projected to the year 2050. 

It is important to keep in mind that the total possible amount of fresh water can never be fully used. There 
is high variability of water resources in space and time. River flow depends upon the seasonal climate. An 
example would be that what is available as snowmelt into the rivers will not be available in the dry season. 

Slide 12: Why is the Water Shortage Projected to Worsen? (Question Slide) 

Discussion Question for Students: Ask your students why they think that water shortages are predicted 
to become worse over time. 

Although there are current supply problems that need to be solved, as shown by slides 9 and 10, the 
increase in demand for water is an even bigger factor. 

This predicted increase in demand for water is based largely on projected population growth. The larger 
the population, the more agriculture is required to feed people. Agriculture currently accounts for about 
70% of the fresh water usage. The other factor that enters into this prediction is the increasing economics 
of currently underdeveloped countries. 

Slide 13: World Population is Increasing 

This graph presents the latest estimates and projections of world population from the U.S. Census Bureau. 
The world population increased from 3 billion in 1959 to 6 billion in 1999, a doubling that occurred over 
40 years. The Census Bureau's latest projections imply that population growth will continue into the 21st 
century, although more slowly. The world population is projected to grow from 6 billion in 1999 to 9 billion 
by 2042, an increase of 50% that is in approximately 43 years. 

Slide 14: In What Ways Would an Increasing World Population Affect Water Consumption? 
(Question Slide) 

This is a good time for students to brainstorm what water is used for and relatively how much water is 
used. The next slide depicts an increase in population. 

Slide 15: Where Clean Water Use is Rising 

This slide depicts the number of cubic kilometers of water withdrawn for municipal, industrial, and agri- 
cultural purposes over a period of 100 years, from 1900 to 2000. 

The most important point is that agriculture requires at least two-thirds of all of the water withdrawn. As 
the graph indicates, all uses of water rise as population increases. 

Slide 16: Trends in Population and Water Use 

This figure shows the two graphs, previously seen, side-by-side, in order to facilitate easier comparisons. 
Students can easily notice that the trends in the increase of population over time parallel the increase in 
water consumption. 

Slide 17: Is There a Relationship Between Poverty and a Lack of Clean Drinkable Water? 
(Question Slide) 

Answer: There are strong correlations between a country's financial wealth and the presence of clean, 
drinkable water. To clean and deliver drinkable water requires expensive infrastructures of cleaning systems 

www.ckl2.org 410 



and pipes to transport the water in areas where water is present in sufficient quantities to meet the 
populations' needs. In areas where there is not enough natural fresh water sources to meet the needs 
(drinking water, sanitation, industry, and agriculture) an expensive system must be employed to remove 
the salt, (desalination), from the water. The World's Water Report says that 1 in 6 people on earth suffer 
from extreme poverty. 1 

The distribution of access to adequate water and sanitation in many countries mirrors the distribution 
of wealth. Access to piped water into the household averages about 85% for the wealthiest 20% of the 
population, compared with 25% for the poorest 20%. 

As an optional activity, you may want students to examine a set of tables with information on different 
countries' water in cubic meters per person and each country's gross national product. Students could 
work in groups to produce a line graph for these two variables. They could share their interpretation of the 
graphs. As a less time-consuming alternative activity, students could simply scan the tables with partners 
to notice the patterns shown by these two variables. 

An important understanding to be developed by students during this study of nanofiltration is that the 
current world water crisis reflects the economic and political decisions made by countries and people. 

Information to design an activity like this is available at: https://cia.gov/library/publications/ 
the-world-f actbook/index . html . 

1 Water: A Shared Responsibility. UN Report, produced by Berghahn Books and United Nations Education, 
Scientific and Cultural Organization (UNESCO). 

Select a country from the menu at the top. 

Slide 18: Countries Differ Widely in their Water Usage 

The next three slides are shown to give students an opportunity to make the connection between a country's 
water usage and per capita wealth. Though for the higher amounts of water usage, there is not an exact 
correlation with wealth; the low wealth countries consistently show low per person water usage. 

This slide depicts a variety of countries' average daily water usage per person between the years of 1998 
and 2002. Some of the countries with especially high water usage and some of the countries with low water 
usage are displayed. For a list of all of the countries' average daily water usage during this same time 
frame, refer to http://www.cia.com. 

Slide 19: Countries Differ Widely in Wealth 

This slide shows the same countries' wealth depicted in terms of purchasing power per person for each 
country in 2005. These figures are from http://www.cia.com. 

Slide 20: Notice Any Correlations? 

This slide displays the countries' average daily water use per person graph, seen on slide 18, superimposed 
on the wealth graph (depicted as purchasing power per person). 

This is a good opportunity for students to look at the data displayed and make statements about the 
relationships from the two variables displayed. If students disagree, it is an opportunity for them to choose 
evidence to support their argument. You might ask them what other information they would need to draw 
a conclusion. 

Question for Students: Is there any evidence that a country's per person water usage has anything to 
do with a country's per person purchasing power? 

Slide 21: Many Without Access Live in Poverty 

This graph shows the approximate total number of people, in millions, who don't have access to sanitation 
(bar on the left) and to clean water (bar on the right). More than two-thirds of the people who don't have 
access to clean water make less than $2 a day. A little over half of the people who don't have access to 

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sanitation make less than $2 a day. 

Slide 22: Impact of Water Scarcity I 

This slide highlights the impact of water scarcity on the human condition, globally. This is a good teachable 
moment. This slide says that 2.3 billion people lack adequate sanitation; slide 9 mentions the estimate of 
2.6 billion people. 

Question for Students: How hard is it to estimate this phenomenon? 

Sanitation and a lack of clean drinking water are related because human feces and urine contain and grow 
bacteria that cause disease in humans. If there is no way of separating this sewage from a fresh water 
source, people will become diseased when drinking this water. 

Slide 23: Impact of Water Scarcity II 

This slide presents additional information from the World Health Organization regarding the impact of 
water scarcity. It also includes a prediction for 2020 if population continues to rise, and fresh water 
availability continues to be scarce. 

The leading cause of death for children in general is associated with respiratory illnesses. The second 
leading cause of death is diarrhea, which is related to unclean water. 

Slide 24: Impact of Water Scarcity III 

This slide shows young women and children carrying water to their homes. The impact on a child's or 
a woman's time in water scarce areas is greater than that on an adult's or a man's, as it is a cultural 
tradition in many regions to assign the task to children (or more often to very young women) of bringing 
water from its source to the home. This can require up to 6 miles of walking a day. 

Question for Students: How would carrying water a few hours each day for your family impact your 
life? What would you have to give up? 

Slide 25: Children Carrying Water 

This is a slide that shows just a few of the amazing pictures publicly available of children carrying water. 

Slide 26: War for Diminishing Resources? 

This slide highlights a controversial prediction among many authorities. Water is not always a renewable 
resource. Most of the water used is found stored naturally underground in aqueducts that have been 
the result of rainwater accumulated over decades, if not centuries. In some regions, like Los Angeles, 
California, the water is being drained from these aqueducts at a faster rate than natural rainwater can 
replace. Further, draining the aqueducts at a fast rate can cause subsidence, the collapsing of the land, 
allowing the ocean to infiltrate and contaminate fresh underground water areas. 

Slide 27: How Can We Address the Water Crisis? 

Agriculture consumes about 70% of fresh water supplies, so efficiencies there — like more efficient irrigation 
methods — could have the most impact. But there are a lot of things that we can do on the smaller scale, 
too, like conserving water at home and in our gardens. Lots of web sites offer water saving tips. A good 
example is http://www.wateruseitwisely.com 

Even eating less meat saves a lot of water. Livestock consume huge resources. Author of The Food 
Revolution, John Robbins, estimates that "you'd save more water by not eating a pound of California beef 
than you would by not showering for an entire year." 

Can we find new sources of water? Not really, but we could treat the undrinkable water that we have. But 
treatment takes energy and requires technology, so it costs money. 

We can't drink salt water or use it for agriculture, but we could treat it to take out the salt using reverse 
osmosis techniques. This is a particularly expensive process, because it requires a lot of pressure (which 

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means a lot of energy) . 

Ground water and waste water this is contaminated can also be cleaned. For example, bacteria can be 
killed by exposing the bacteria-laden water to UV light and chlorine. We can also clean water by filtering 
it. 

Slide 28: Use Filters to Clean Water 

Water can be cleaned by pouring it through pebbles, sand, and charcoal. Membranes can also be used to 
filter out small particles. A membrane is a structure that lets some things through and others not. You 
may want to check that your students know what a membrane is. 

An efficient method of cleaning water is to use a series of increasingly smaller filters that filter out increas- 
ingly smaller particles. This picture highlights the membranes that clean water and the particles that each 
type of membrane removes. In general, the smaller the membrane, the more pressure is needed to push 
the water through the membrane, and the more expensive is the process. Usually larger membranes are 
used as prefilters to filter out the larger particles that would easily clog or "foul" the smaller membranes. 

Slide 29: Can Nanotechnology Help? 

Nanotechnology is a new area of engineering in which many laboratories are working to create innovatively 
designed membranes that have a hope of filtering water more cheaply and more flexibly that those currently 
on the market. 

Slide 30: Questions 

The questions on this slide guide this unit. Though the unit is built around solving the polluted water 
problem for the town of Jarny, students should also learn something about water purification processes 
and the basic science of water. This understanding will help them to reflect knowledgably on the global 
health problem of a lack of clean drinking water. 

Resources 

The World Water Forum is a group that has met for the fourth time to consider issues related to global water 
scarcity and fresh water sustainability. The fourth one was attended by governmental delegations from 
148 countries, 200 legislators, 160 representatives of local authorities, 185 children, and a plethora of non- 
governmental organizations, UN agencies, experts, academia, water managers, and media representatives 
who met in Mexico City from March 16 through March 22 to share their local experiences, in order to make 
a difference in a world in which billions of people still lack access to safe water and sanitation. This group 
has published a report that highlights the conclusions and agreements made during this conference. The 
final report can be found at http://www.worldwaterforum4.org.mx/files/report/FinalReport.pdf. 

Water Crisis: Student Data Worksheet Teacher Instructions &; Answer 
Key 

This activity allows student to become actively involved in interpreting the different figures and graphs 
that are used in the Water Crisis PowerPoint presentation. Providing them with an opportunity to think 
about what each representation means before presenting the slides will allow for greater engagement on the 
part of your students and develop their graph interpretation skills. You may want to assign this worksheet 
as a homework assignment before you show the slides, or have students fill out the worksheet as you come 
to each of the slides, but before discussing them. 

Note: Figure 2 is more easily distinguished in color, so you may want to pass out color copies of the 
student worksheet to your students. Otherwise, students may need to see the slide presentation to answer 
the questions associated with Figure 2. 

Directions 

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Using the graphs and maps, answer the following questions. This activity will give you the opportunity 
to interpret some of the graphs and maps that you'll see during the Water Crisis slide presentation during 
class. 



Distribution of Larth's Water 



Tr.-sli 




Fjrtti's water 



Othei o.«)% 




Freshwater 



"urliut! 
»vn( a 




Fresh 
surface wdtnr 

(liqilirl) 



Figure 3.25: Distribution of earth's water. 

1. According to the bar graphs in Figure 1, what percentage of the world's water is fresh water? 

3% 

2. What do these three divided bar graphs tell you about where the Earth's fresh water resides? 

The earth's fresh water resides in icecaps and glaciers, ground water, lakes and swamps and rivers. 

Physical water scarcity refers to the lack of water to meet domestic, industrial, and agricultural needs. 
Areas of physical water scarcity are shown in red on the map in Figure 2 below. Economic water scarcity 
means that an area or country has insufficient financial resources to deliver safe, clean water to those areas 
that need it for drinking or agriculture. Areas of economic water scarcity are shown in orange in Figure 2. 

Answer questions 3-8 based on information from the map in Figure 2. 

2. Name the countries or global areas that are experiencing physical water scarcity. 

In Northern Africa: Algeria, Libya, and Egypt. In the Middle East: Saudi Arabia, Iraq, Turkey, Iran, 
Pakistan, Afghanistan, much of India, Northern China and some smaller countries. 

3. What would you predict the climate to be in these areas and why? 

These areas would most likely have hot and dry climates, because the map indicates they have a physical 
water scarcity. 

4. Name the countries or global areas that are experiencing economic water scarcity. 

Central and most of South American, central and much of southern Africa, China, Viet Nam, Laos, 
Cambodia, the Philippines and the rest of the East Indies, and Australia. 

5. Name the countries or global areas that are not experiencing any water scarcity. 
North American countries and Northern Eurasia. 

6. What do you predict the difference in per capita income (average income per person) would be between 
regions with plenty of water and regions with economic water scarcity? 

Because water is needed for personal, industrial and agricultural use, it makes sense that those countries 



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414 




■ Phytic* water scarcity 

■ Economc water scarcity 

■ Sufficient water 

•.jt Estimated 



Figure 3.26: Global map of water scarcity in 2006. 



with greatest access to water are among the wealthiest nations as well. 

7. The southwestern United States is typically characterized as having a dry, arid climate. Why might 
this region be shown as having plenty of water even if it is dry and arid? 

Students may guess, correctly, that we divert water from northern rivers to the southern drier lands. They 
may also guess that there are rich sources of underground aquifers that supply water. 

When water is taken from a natural source for human use, it is called "water withdrawal." However, a 
country can never withdraw all of the fresh water that is theoretically available within its borders. Much 
of it is seasonal, or part of flood runoff, or rain that cannot possibly all be captured. Countries that 
withdraw a high percentage of their available fresh water are said to be under "freshwater stress" and are 
in danger of becoming considered "water scarce." In the map in Figure 3, the light orange represents mild 
freshwater stress and the darker orange represents extreme fresh water stress. Blue areas are considered 
to be free from freshwater stress. 

8. Compare the two maps above, showing freshwater stress from the year 1995 and projected to the year 
2025. What are the changes that you see happening in which areas? 

America and Alaska go from a water withdrawal of 10 - 20% to 20 - 40%, as does Mauritania and the 
Sudan in Central Africa. China also increases its' water use. Experiencing over 40% of water withdrawal 
now is Uganda, South Africa, and India. 

9. In Figure 4, what trend do you see in for the global population? 
The population increases by three times from 1950 - 2050. 

10. What would you predict the global population to be in 2060? Justify your prediction. 

The population would likely increase to 10 billion people, based on the trend depicted for the previous two 



415 



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1995 



Freshwater Stress 




2025 





Water withdrawal as percentage of total available 

H Over 40% Hi 20% -10% 

40%-20% M Lessthan 10°o 

: 



Figure 3.27: Global map of freshwater stress, 1995 and 2025 (predicted). 



10 - 


Wor 


d Population: 1 

1 7 " " T " 


950-2050 


9 - 

— * H - 






















9 Billion 


£ 7 
















"~8 Billion 






O 1 

~ fi - 














7 Billion 








e e 

c 5 - 

i« 

3 3 - 
a. J 

,? 5 










s*"^ 


3 Bill 


XI 
















** 5 


Bilio 


1) 












4 Bilion 














"""" 3 Billion 














Q. ^ 

1 
























- 












































c 


3000QOOOQOQ 


i 


itDt^oooO'-rMcoTj-tr) 


c 


)0>030)0>OOOOOO 








Year 


Source: U. 


S. Census OutftAu. lni«iii.»Hinij»l Data Base, August ?006 version 



Figure 3.28: World population from 1950 to 2050 (predicted). 



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416 



decades. 



Global Annual Water Withdrawal by Sector. 1900-2000 



6.000 
4.500 

■ 

jg 3500 
O 3000 
?500 




.5i 2000 



1800 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 
Source: Abramovitz 1 996 ( 1 ) 

Figure 3.29: Global annual water withdrawal by sector, 1900-2000. 



11. According to the graph in Figure 5, which sector uses the most water? 
Agriculture 

12. Which sector uses the least amount of water? 
Domestic 

13. How does the trend in water consumption (Figure 5) compare to the trend in population (Figure 4) 
for the time period 1950-2000? 

The trends parallel each other. 

Average Daily Water Use Per Person (1998-2002) For Selected Countries 



Average Daily Water Use Per Person (1998 -2002) 
For Selected Countries 



Liters of Water 
600 t 



500 
400 






m 













& 



^ 



Figure 3.30: Average daily water use per person for selected countries, from 1998 to 2002. 

14. According to Figure 6, which countries consume the most water? 
United States, Australia, Italy, Japan, Mexico, Spain, France and Austria. 

15. Which countries consume the least water? 



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China, Bangladesh, Kenya, Ghana, Cambodia, Ethiopia, Haiti, and Mozambique. 



Average Wealth (Purchasing Power Per Person in 2005) 
For Selected Countries 

Purchasing Power Per Person 






■ $40,000 
$35,000 
$30,000 

■ $25 000 

$:c coc 

ri- mi 

■ $10,000 

■ $5,000 
































































































1 a 


















Ill 1 ...... . 




V? ^A oS 1 tP ■*" r* & CA A^ 0^ & & & C$* £> & <$ i\* \* ^ -P 



Figure 3.31: Average wealth for selected countries (purchasing power by person in 2005). 

Answer questions 16-19 based on information from the graph in Figure 7. 

16. How many countries have an average per person purchasing power of less than $10,000? 
13 

17. How many countries have an average per person purchasing power of more than $25,000? 
9 

18. How many countries have an average per person purchasing power of $10,000 - $25,000? 
Zero 

19. What is the difference between the average per person purchasing power in the highest wealth country 
and the lowest wealth country? 

About $41,000/year 



Average Daily Water Use Per Person (1998-2002) & 
Wealth (Purchasing Power Per Person in 2005) For Selected Countries 



Litres of water | 
600 - 



400 
300 

200 



It 



rl 



in 



] 



I Purchasing Power Per Person 

$45,000 
$40, DOC 
$35,000 
$30,000 
$25,000 
$20,000 
$15,000 
$10,000 
$5,000 



f* 



^^^m^i^^wm^^ 



<r^ 



j? 



Figure 3.32: Average daily water use per person and wealth. 

20. According to Figure 8, does there seem to be a relationship between a country's wealth and their 
average daily water consumption? If so, what is the relationship? 

In most cases, with a few exceptions, the amount of wealth determines the amount of water consumption. 



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418 



In other words, the greater the wealth of a nation, the more water it consumes, and conversely, the less 
wealth a nation has, the less water it consumes. 

Fine Filters Initial Ideas: Teacher Instructions 

The goal of this exercise is to have your students "expose" their current ideas about the current and future 
availability of water on a global basis before they engage in learning activities that will explore these 
questions. You should let your students know that this is not a test of what they know and encourage 
them to make guesses which they will be able to evaluate based on what they learn in the unit. You may 
also want to have your students share their ideas with the class (there are no "bad" ideas at this stage) 
and create a giant class worksheet of ideas. Students can then discuss whether or not they think each of 
these statements is true and why. 

Write down your initial ideas about each question below and then evaluate how confident you feel that 
each idea is true. At the end of the unit, we'll revisit this sheet and you'll get a chance to see if and how 
your ideas have changed. 

Table 3.12: 



1. What are wa- How sure are you How sure are you How sure are you End of Unit Eval- 



ter's unique prop- 
erties so important 
for life as we know 
if? 



that this is true? that this is true? that this is true? uation 



Not sure 



Kind-of-Sure 



Very Sure 



2. How do we How sure are How sure are How sure are End of Unit 

make water safe you that this is you that this is you that this is Evaluation 

to drink? true? true? true? 

Not sure Kind-of-Sure Very Sure 



3. How can How sure are How sure are How sure are End of Unit 

nanotechnology you that this is you that this is you that this is Evaluation 

help provide true? true? true? 

unique solutions 

to the water 

shortage? 

Not sure Kind-of-Sure Very Sure 



4. Can we solve How sure are How sure are How sure are End of Unit 

our global water you that this is you that this is you that this is Evaluation 

shortage prob- true? true? true? 
lems? Why or 
why not? 

Not sure Kind-of-Sure Very Sure 



419 



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The Water Crisis: Quiz Answer Key 

Write down your ideas about each question below. 

1. What does it mean to have "clean fresh drinking water"? 

Drinking water that does not contain salt or other contaminants that would be harmful to human health. 

2. Explain the term "water scarcity." 

Water scarcity means that there is not enough water to support water for drinking, industry, agriculture 
or environmental ecosystems. 

3. Does water scarcity have an impact on human health? If so, what are some of the consequences? 

Yes. In places of water scarcity, 80% of all child death under the age of five is related to diseases associated 
with a lack of clean water. Contaminated drinking water can cause severe diarrhea, a variety of other 
gastrointestinal disorders, and cause the accumulation of life disabling or fatal toxins in body tissues. 

4. Describe three reasons why some nations are experiencing a scarcity of clean drinking water. 

1. There is not enough physical water available to support a nation's needs for its population. 

2. There is not enough money to deliver the water to the places that need it for drinking or for agricul- 
ture. 

3. There is not enough money to clean the water to make it usable for drinking or for agriculture. 

5. Why is the water scarcity problem projected to increase? 

Water scarcity is projected to increase as population increases and puts more demands on water to meet 
the basic needs of people. 

As underdeveloped countries become more industrialized, the trend is to consume more food that requires 
more water to produce. 

6. Which sector — domestic, industrial, or agriculture — consumes the most water? 
Agriculture. 

The Science of Water 

Contents 

• Introduction to The Science of Water: Teacher Lesson Plan 

• The Science of Water: PowerPoint with Teacher Notes 

• The Science of Water Lab Activities: Teacher Instructions 

• The Science of Water: Quiz Answer Key 

• Reflecting on the Guiding Questions: Teacher Instructions 

The Science of Water:Teacher Lesson Plan 

Orientation 

Water is one of the most unique and ubiquitous substances on our earth. Water's structure and properties 
account for many of the phenomena in our bodies and on our earth. This lesson reviews some of the science 
basics of water. If your students have not yet had a chemistry class, they may find some of this information 
overwhelming. These lessons are not intended to take the place of chemistry, where more intensive study 
is devoted to the variety of topics reviewed here. 

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• The Science of Water PowerPoint slide set introduces the structure of water that accounts for water's 
unique properties based on the quantum mechanical model of the atom, the shape of the water 
molecule and the distribution of charge. 

• The Science of Water Lab Activities are set-up as lab stations. Their overall purpose is to give the 
students hands-on opportunities to experience some of the properties of water. Students may move 
through the stations throughout one or two periods, depending upon your schedule. You may also 
choose to eliminate one more of the stations to save time. Two of the stations are paper-pencil 
activities, and have no special requirements for lab equipment. 

• The Reflecting on the Guiding Questions Worksheet asks students to connect their learning from the 
activities in the lesson to the driving questions of the unit. 

• The Science of Water Student Quiz can be used as a formative or summative assessment of stu- 
dent learning through homework, an in-class group activity, or as an in-class individual assessment, 
depending on your goals. 

Essential Questions (EQ) 

What essential questions will guide this unit and focus teaching and learning? 

(Numbers correspond to learning goals overview document) 

1. Why are water's unique properties so important for life as we know it? 
Enduring Understandings (EU) 

Students will understand: 

(Numbers correspond to learning goals overview document) 

2. As a result of water's bent shape and polarity, water has unique properties, such as an ability to dissolve 
most substances. These properties are responsible for many important characteristics of nature. 

Key Knowledge and Skills (KKS) 

Students will be able to: 

(Numbers correspond to learning goals overview document) 

4. Describe the basic structure and charge distribution of water. 

5. Explain how hydrogen bonding accounts for many of water's unique properties. 

Table 3.13: The Science Of Water Timeline 

Day Activity Time Materials 

Day 1 (50 min) Show the Science of Wa- 50 min The Science of Wa- 
ter PowerPoint Slides, ter PowerPoint Slides & 
using the question slides Teacher Notes 
and teacher's notes to Computer and projector 
start class discussion. 



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Table 3.13: (continued) 



Day 



Activity 



Time 



Materials 



Day 2 (50 min) 



Day 3 (35 min) 



Students work in pairs 50 min 
or small groups at the 
Science of Water Lab 
Activities. Tell students 
to follow the posted 
directions to complete 
the lab at each station, 
moving to the next sta- 
tion when the current 
one is completed. Each 
student should com- 
plete their own Student 
Worksheet, although 
they may consult with 
other group members 
or the teacher. 

Homework: Have stu- 10 min 
dents fill out the Re- 
flecting on the Guid- 
ing Questions: Student 
Worksheet 

Have students work in 10 min 
pairs or small groups to 
discuss their reflections 
on the Guiding Ques- 
tions 

Bring the class together 10 min 
to have students share 
their reflections with 
the class. 

This is also a good 
opportunity for you to 
address any miscon- 
ceptions or incorrect 
assumptions from stu- 
dents that you have 
identified in the unit up 
till now. 



The Science of Water 
Lab Activities: Stu- 
dent Directions posted 
at each Lab Station. 
Photocopies of the Sci- 
ence of Water: Student 
Worksheet 



Photocopies of Reflect- 
ing on the Guiding 
Questions: Student 

Worksheet 

Student's copies of 
their Reflecting on 
the Guiding Questions 
Worksheet 



Administer the Science 
of Water: Student Quiz 
during class, as an indi- 
vidual or group exercise, 
or as homework. 



15 min 



Photocopies of The Sci- 
ence of Water: Student 
Quiz 



The Science of Water 



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422 




We are surrounded by water; we are made of water 
Water in our World 




Figure 3.33 



Water is necessary for life 

Water in our atmosphere helps to keep the planet warm 

Our bodies are composed of and dependent on water 



A Quick Overview 

Of some of the science basics 

What are some of the properties of water that make it so essential to life on our planet? 

All Matter is Composed of Atoms 

• The atom is composed of 

— A nucleus made of neutrons and protons 

— An electron "cloud" composed of electrons 

• Protons and neutrons have nearly identical masses, but their charge is different 



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neutron 



protod 
neutron 




Representation of a nucleus 



Figure 3.34 



Protons have a positive (+) electrical charge and neutrons do not have an electrical charge 



Table 3.14: Subatomic Particles Composing the Atom 



Subatomic Particle 



Charge 



Size 



Location 



Proton 


+ 1 


Neutron 





Electron 


-1 



1 
1 





Part of the nucleus 
Part of the nucleus 
Electron "cloud" (out- 
side of the nucleus) 



The Quantum Atom 






■ 



Nucleus 




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Red dots represent 
areas of probability 



424 

Figure 3.35 



We can only describe areas of probability where we might find an electron 




Figure 3.36 

— Can you predict accurately where the next dart you throw will go? 

— Can you predict an area where the next dart is likely to go? 

Question 

Why do we care about what atoms are made of? 

Electric Charge 




" 





Like charges repel 




Unlike charges attract 

Figure 3.37 

• Electric charge is a basic force that causes movement 
Net Charge of an Atom or Ion 

• The charge on any substance is a result of the total number (#) of 

— Protons (p) + charges, in the nucleus, and 



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— Electrons (e~) - charges, outside the nucleus 
If the # of... then the net charge is.... 

— p = e~ neutral(atom) 

— p > e~ positive(ion) 

— e~ > p negative(ion) 



Atoms Bond 



The electrons experience a force of altraction from 
both nuclei This negative positive negative 
attraction holds the two particles together 




Ekfdrur doud 



This attraction is called a chemical bond 
one part of electrons constitutes ONE bond 

Nature always wants to be 
in the lowest energy state! 

Figure 3.38 



• The outer electrons of both atoms are mutually attracted to the nuclei 

— Oppositely charged particles form a bond, representing a lower energy state for each of the 
atoms, releasing energy 

Why are Bonds Formed? 

Bonds are formed because of the electrostatic attraction between atoms. 

In doing so, the atoms achieve a lower energy state. 

Ionic Bond: Chlorine (Blue) Grabs Electron from Sodium (Red) 

Forming a Water Molecule 

• Unequal attraction to bonding electrons 

— Oxygen is a strong electron grabber (high electronegativity) 

— Hydrogen's electron cloud tends to hang out close to oxygen, leaving H's positively charged 
nucleus all by itself 

Electron Density is Uneven 

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Click the image above to view the animation in your web browser, or 
go to http://nanosense.org/download/finefilters/Nacl_SD.mov 

Figure 3.39 

Orbital representations of 
hydrogen and oxygen 



k+ 




•:;■<}.' 







A water molecule 



Figure 3.40 



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Hyjrogen 




Etectncde 



A water molecule, with 
electron density represented by 
the shaded blue areas 

Figure 3.41 



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428 



The average electron density around the oxygen atom in a water molecule is about 10 times greater 
than the density around the hydrogen atoms 

— This non-uniform distribution of positive and negative charges, called a dipole, leads to the 
substance's unusual behavior 



Water is a Polar Molecule 



More positive ends 




More negative end 

A water molecule 

5- means partial negative charge 
5+ means partial positive charge 

Figure 3.42 

• The unequal distribution of charges on the water molecule make it a polar molecule 

— One end is more negative, and one end is more positive 

Hydrogen Bonding I 

• The partial negative end of the oxygen atom is attracted to the partial positive end of the H atom 
on an adjacent molecule 

• Hydrogen bonds give water its unique properties 

Hydrogen Bonding II 

Hydrogen Bonding Representation 

• In water, hydrogen bonds form between the partially negatively charged oxygen atom and the par- 
tially positively charged hydrogen atom 

Unique Properties of Water 

• Universal solvent 

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Hydrogen bonding between 
water molecules 





' Hbond 



Figure 3.43 



closer look at WStCF 




Topics covered in this movie: 

• the polarity of water 

• hydrogen bonds 



start movie( 



Figure 3.44 



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430 




Hydrogen 

bond 



(length appears drflorcnt for porspactvo 1 30] I 






Water molecules, with the 
hydrogen bonds represented by 
the dotted lines 



Figure 3.45 



• Exists in nature as a solid, liquid, and gas 

• The density of ice is less than liquid water 

• High surface tension 

• High heat capacity 

• Exists as a liquid at room temperature 

High Surface Tension 




Figure 3.46 



Allows water to form drops 



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• Allows water to form waves 

• Water drops can "adhere" to surfaces even though gravity is pulling on them 

Can You Explain Why this Drop Sticks to the Leaf and Grows Larger? 




Figure 3.47 



Or How this Spider Can Walk on Water? 




Figure 3.48 



Adhesion 



Adhesive forces are attractive forces that occur between two unlike substances 
In a narrow glass tube 

— Water molecules are more strongly attracted to the tube than they are to each other (cohesion) 



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432 




Figure 3.49 



The cup shape formed at the top of the water is called a meniscus 



Water Climbs Trees! 




Water 



Figure 3.50 

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• Evapotranspiration 

— The tiny tubes in the root hairs suck up water from the soil 

— Inside the plant are more hollow tubes (xylem) for transporting water through the plant 

— Finally, water exits the plant through the tiny openings in its leaves (stomata) 

High Specific Heat Keeps Beaches Cooler in the Day and Warmer at Night! 




Figure 3.51 

• Specific heat 

— The amount of energy required to change 1 gram of a substance \°C 

• Water has high specific heat 

— Absorbs large amounts of heat energy before it begins to get hot 

— Releases heat energy slowly 

— Moderates the Earth's climate and helps living organisms regulate their body temperature 

Solid, Liquid, and Gas 

• Water is the only substance which exists under normal conditions on earth as a solid, a liquid, and 
a gas 

Ice is Less Dense than Water I 

Density of H2O at different temperatures 



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Figure 3.52 




Figure 3.53 



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Table 3.15: 



Temperature °C 



Density g/cm" 



(solid) 

(liquid) 

4 

20 

100 (gas) 



0.9150 
0.9999 
1.0000 
0.9982 
0.0006 



Ice is Less Dense than Water II 





Crystal lattice structure of ice 



Ice crystal 



Figure 3.54 



• This is a very rare property! 

Questions 

Can you imagine if ice did not float? 

How do you think that would affect the world? 

Ice Melting 

• Notice that ice has an open lattice structure that collapses when it melts 
Water is a Universal Solvent 

• Water is a polar molecule with one end more positive and one end more negative 

— Being polar allows water to dissolve nearly any substance with an unequal distribution of charges 

— Water is the best substance that is universally used for transporting dissolved substances 

Important Points 

• What are water's unique properties? 

• What is water's structure, and how does it cause these properties? 

• What would our world or life be like without water? 



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Figure 3.55 




Water dissolves more 
substances than any other 
liquid 



Figure 3.56 



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The Science of Water: Teacher Notes 

Overview 

This presentation gives students a sense of the structure of water in terms of its shape and charges. The 
traditions of science have been represented here to give students a picture of how modern science talks 
about the structure of atoms and charge distribution. Several representations of water are included in this 
slide set. The big "take away" for students is that hydrogen bonding creates stronger than normal (for 
substances of a similar molecular mass) bonds between water molecules. Those relatively strong bonds are 
the reason we see water's unusual properties: high surface tension, high boiling temperature, adhesion, 
cohesion, low vapor pressure, high specific heat, "universal solvent," the density of the solid form being 
less than that of the liquid form, and being a liquid at room temperature. 

Students may have difficulty with some of the ideas represented in these slides, depending on their back- 
ground. If students have a weak background in chemistry, it is suggested that the emphasis in these 
slides be on the shape and charge distribution of the water molecule as it relates to the above-mentioned 
properties of water. 

Slide 1: The Science of Water 

Ask students to think about where water is in this world, and what forms water comes in (solid, liquid, 
gas). Tell students that the focus of this lesson is on the special structure and characteristics of water that 
make it such a unique substance, a substance that we all depend upon for living. 

Slide 2: Water in our World 

Our planet is habitably warm because the sun's rays (electromagnetic radiation), filtered through the 
atmosphere, collide into the earth. When they reach the surface of the earth, the earth absorbs some of 
the rays, heating the earth. Some of the sun's rays are radiated back into the atmosphere as longer energy 
waves, infrared rays or heat. The gases in our atmosphere "trap" these energy waves, preventing them 
from escaping our atmosphere. The earth would be impossibly cold to live upon without this phenomenon, 
known as the "greenhouse" effect. Water is one of the greenhouse gases. There is much current concern 
over the amount of greenhouse gases entering the atmosphere and heating our planet to a growing degree. 
The emphasis of this attention has been mostly on the gases emitted from the combustion of fossil fuels, 
in other words, man's contribution to greenhouse gases as a result of using gasoline to fuel vehicles. 

The human body is composed of water, among other substances. The total amount of water ranges from 
50-80%, depending on age, amount of fat present, and other factors. The usual figure used for the amount 
of water in the normal adult body is 70%. Water is a major component of our blood, our lymph, our serous 
membranes, and other structures. 

Slide 3: A Quick Overview 

This set of slides presents a quick overview of the science of water. Each of the topics touched upon, such 
as models of the atom, bonding, charge distribution, physical properties, and chemical properties are big 
topics themselves. This set of slides is intended to present an overview only. 

Discussion Question for Students: What are some of the properties of water that make it so essential 
to life on our planet? 

You may want your students to brainstorm what they already know about water's unique properties. This 
is a good way to reveal students' prior knowledge and to uncover any misconceptions about the properties 
of water. 

Slide 4: All Matter is Composed of Atoms 

Most students have heard about the particles that compose the atom, as well as the basic structure. They 
probably will know that the nucleus, while being very, very small compared with the overall volume of an 

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atom, comprises the mass of an atom. The neutron and proton are nearly identical masses compared with 
the negligible mass of an electron. 

The purpose of this slide is to build knowledge about water's unique structure, starting from the basics, 
with an emphasis on the charge characteristics of a water molecule. The structure to emphasize in this slide 
is the positively charged nucleus (of a "generic" atom). This will determine the overall charge distribution 
as well as the net charge on atoms joined together to form molecules. 

Slide 5: Subatomic Particles Composing the Atom 

This chart represents a simplified version of the relative size, location, and charges of the proton, neutron, 
and electron. 

For reference, a proton has a mass of 1.672 x 10 -27 kg and a charge of +1, a neutron has a mass of 
1.675 x 10~ 27 kg and no charge. An electron has a charge of -1 (the same magnitude as a proton's charge, 
but opposite in direction). The electron is described as having characteristics of a particle and a wave, 
depending upon the situation. (The photoelectric effect demonstrated by Einstein illustrates the particle 
behavior of an electron and Young's double slit experiment demonstrated an electron's wave behavior.) 

All things point to the electron having no measurable size at this time, although our ability to measure 
incredibly small objects is limited. 

Slide 6: The Quantum Atom 

Again, the electron cloud representation as determined by quantum mechanics is shown here. The big 
points are: 

1. The dots that represent the orbital cloud indicate a probability distribution of where an electron 
might be found. The more dense areas of the cloud represent areas of higher probability. The less 
dense, as depicted by the decreasing density of dots as one moves farther away from the nucleus, the 
less probability there is of finding an electron. 

2. Electrons are constantly moving really, really fast. That means that the electric charge they carry is 
moving really, really fast as well. This overall or "net" electric charge distribution is what determines 
all bonding. 

3. Electrons have a "quanta" of energy. Bohr learned that electrons could gain or lose only a specific 
quantum of energy. To illustrate this, think about a glass that you can fill with water, and stop 
filling at any position. Electrons are not like that. You may only "fill" by specific increments. These 
increments are individual to each electron in each atom. They can be measured when an electron 
"loses" energy by releasing a photon of light. This photon of light can be measured in terms of its 
wavelength, making it possible to determine its energy. 

Slide 7: Probability 

This slide is to help students to visualize the idea of a probability distribution in a more concrete way. 

Slide 8: Question Slide 

Questions for Students: What do students think? Why do we care about what atoms are made of? 

This is another time that, within a class discussion, you may be afforded the opportunity to see what 
students understand and the discussion may allow any misconceptions to surface. Misconceptions are 
important to address, as they are very powerfully embedded in students' understanding of the world. They 
are resistant to being replaced with more accurate scientific information. 

Slide 9: Electric Charge 

Traditional curriculum underemphasizes the role of electric charge in chemistry. Often forces are addressed 
in physical science curriculum during middle school classes or in physics as an advanced course in high 

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school. It is important for students to realize that these "swarms" of electrons represent an attractive (to 
positive charges) and repulsive (to negative charges) moving force. This is a very dynamic concept. 

Slide 10: Net Charge of an Atom or Ion 

This slide is to remind students that the net charge of an atom comes from the total amount of protons 
(positive charge) in the nucleus and the total amount of electrons (negative charge) in that atom. In 
addition to that, there may be an equal distribution of electric charge around some atoms, resulting in a 
polar molecule (a molecule that has a separation of charges). 

Slide 11: Atoms Bond 

This slide focuses on how opposite charges will form a bond and that a bond between two atoms represents 
a lower energy state for both of the atoms bonded together than if they were not bonded. Students may or 
may not know this. One of the laws of nature is that matter will always move to the lowest energy state 
possible. The lowest energy state is the most stable position for matter to obtain. 

Slide 12: Why are Bonds Formed? 

This slide highlights again that bonds are formed because of the attraction of oppositely charged particles. 
What causes atoms or particles to have opposite charges is not covered by this unit. That is another 
extensive subject that is beyond the scope of this slide set. This subject is a typical component in college 
preparatory chemistry. 

Slide 13: Ionic Bond: Chlorine (Blue) Grabs Electron from Sodium (Red) 

This is an animation that depicts a bond forming between sodium and chlorine. It is just to give students a 
sense of the swirling, moving electrons as the two atoms are held in close proximity. The video clip should 
play automatically when in the "view presentation" mode. If it does not play, click on the image to view 
the animation in your web browser. 

Slide 14: Forming a Water Molecule 

This is a depiction of the orbital representation of two hydrogen atoms and an oxygen atom, bonded, and 
their distribution of charges when they come together to form a water molecule. 

The slide mentions "electronegativity." Electronegativity is a man-made composite value of the relative 
amount of each of the elements to attract an electron to itself. To obtain this value, several measures of 
each of the atoms are considered: first and second ionization energies, disassociation energy, and electron 
affinities. Linus Pauling was the first among many others to create this value. It has trends in the periodic 
table. Four is the highest electronegative number, assigned to fluorine, while one is the lowest. 

To determine the type of bond that two atoms make, one must subtract the electronegative value of each 
atom. Though this is a continuum scale, if this difference is approximately 0.5, the bond is considered a 
non-polar covalent. If the difference is between 0.5 and 1.6 (this varies), then the bond between the two 
atoms is a polar covalent one. If the difference in the electronegativity values of the two atoms is greater 
than 1.6 (or so) then the bond is an ionic bond. 

Slide 15: Electron Density is Uneven 

This slide depicts the density of the distribution of negative charges on the water molecule. This representa- 
tion is somewhat controversial on the part of teachers. Some students expressed liking this representation, 
however, because it helped them to visualize an uneven distribution of electrons. The shaded area repre- 
sents the strongest distribution of negative charges and the lighter areas represent the lower distribution of 
negative charges. The big point of this slide is to communicate the idea that on the water molecule there 
is a partial positive end and a partial negative end. 

Slide 16: Water is a Polar Molecule 

A more detailed picture of the water molecule further illustrates the previous slide. If students have not 

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seen the symbol S + (partial positive charge) and 8 (partial negative charge), this would be a good time 
to explain these commonly used symbols. 

Slide 17: Hydrogen Bonding I 

Hydrogen bonding occurs in small molecules with a highly electronegative nonmetal element (N, CI, O, F) 
that bonds with hydrogen. The attraction of hydrogen's lone electrons toward the highly electronegative 
atom results in a separation of charge on the molecule. Water is the most famous case of this. Hydrogen 
bonding occurs between adjacent molecules. While it is weaker than ionic or covalent bonding, which 
occurs between atoms to form molecules or ionic compounds, it is a stronger bond than Van der Walls 
forces that occur between adjacent molecules. 

Slide 18: Hydrogen Bonding II 

This is a clever animation that illustrates hydrogen bonding. If you have a hard time enabling the link 
embedded into this PowerPoint slide, try: 

http://www.northland.cc.mn.us/biology/Biologyllll/animations/hydrogenbonds.html 

Slide 19: Hydrogen Bonding Representation 

The water molecule in the center shows the partial positive and negative charges. The illustration on the 
right depicts these charges among several individual water molecules that are bonded (represented by the 
dotted line) negative end to positive end. 

Slide 20: Unique Properties of Water 

Although there are more unique properties of water, the ones listed on this slide are generally thought to be 
the most important. This slide will serve as an introduction to these properties. Each of these properties 
is explained further in the following slides. 





Figure 3.57: Surface of water with forces that prevent a particle from sinking (left) and forces of two water 
molecules (right). 

Slide 21: High Surface Tension 

This slide introduces the concept of surface tension. One way of describing surface tension is to point out 
that sometimes water acts like a "skin." This results from the surface water molecules clinging to each 
other and NOT to the air molecules over them. 

The images in Figure 1 above are two different representations of surface tension. The image on the left 
shows the surface of water with forces strong enough to prevent a particle from sinking. The image on the 
right shows the forces of two water molecules. The water molecule at the surface has fewer force arrows 
attracting it to the other water molecules than the water molecule below it that is surrounded on all sides 
by other water molecules. 

Slide 22: Question Slide 

Question for Students: Can you explain why this drop sticks to the leaf and grows larger? 



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Ask students to explain how water forms drops AND how water sticks to the leaf, instead of gravity pulling 
it down. 

Slide 23: Question Slide 

Question for Students: Or how this spider can walk on water? 

The spider has very light feet that don't "puncture" the water. The water behaves like a skin, buoying up 
the spider. 

Slide 24: Adhesion 

Adhesion occurs when the water molecules are more attracted to the sides of a small diameter tube than 
they are to each other. This accounts for phenomena like the meniscus in tubular glassware, or for the 
capillary action that draws water up into the xylem (small tubes throughout a plant that transmit water) 
of a plant. 

Slide 25: Water Climbs Trees! 

The basis of water moving through plants is that, like a small graduated cylinder, water is more attracted to 
the sides of the plants than to other water molecules. The water climbs up the plants' tubes for transporting 
water (xylem), and the water molecules attach to each other, pulling them along as well (cohesion). 

An additional assignment would be to have students use ChemSense (chemsense.org) to animate water 
molecules moving through a plant. Another would be to have students illustrate, at the molecular level, 
water moving through a plant. 

Slide 26: High Specific Heat Keeps Beaches Cooler in the Day and Warmer at Night! 

Definition: Specific heat is the amount of energy required to change 1 gram of a substance 1° Celsius. 

Water has a relatively high specific heat. This means that it will absorb a lot of heat energy before raising 
the temperature of the water. If you live near a large body of water, the air temperature will not be as 
hot during the day. The water absorbs a lot of the heat, making air temperature milder than it is inland. 
When the sun goes down, the water slowly releases the heat that it has absorbed during the daytime. The 
night air temperature is warmer than the air inland. Climates are milder near large bodies of water than 
they are away from water. 

Warm-blooded animals regulate their internal temperatures by being composed of large amounts of water. 
This water is slow to heat and slow to cool, moderating temperatures from outside of the body to inside 
the body. During periods of extreme heat, animals can release heat by sweating. The sweat on the outside 
of the skin absorbs energy as it evaporates off of the skin, cooling the temperature of the skin beneath the 
sweat. 

Slide 27: Solid, Liquid, and Gas 

Have students think about any other substance that is found naturally on earth in more than one phase 
of matter. Water is the only one to exist naturally in all three phases. 

Slide 28: Ice is Less Dense than Water I 

This table illustrates that water is the most dense at 4°C Have students examine the figures for the density 
of water at different temperatures. 

Slide 29: Ice is Less Dense than Water II 

This slide is just a visual to illustrate a macro-picture of an ice crystal and a nano-picture of ice as a 
solid. The crystal lattice structure of ice literally expands the structure of water as a solid, which will then 
collapse and become denser when melted. 

Slide 30: Question Slide 



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Questions for Students: Can you imagine if ice did not float? How do you think that would affect the 
world? 

Slide 31: Ice Melting 

Click on the image to view the animation in your web browser. This will show the water molecules losing 
the bonds between them, collapsing and moving faster as the phase changes from solid to liquid. 

Slide 32: Water is a Universal Solvent 

Water is often described as a universal solvent. This is not really accurate. Water can dissolve polar 
or ionic substances. Water cannot dissolve nonpolar substances. Water's positive end and negative end 
have nothing to be differentially attracted to in a nonpolar substance. Water also cannot dissolve ionic 
substances that are more attracted to each other than they are to the overall force of the water molecules 
that surround the ions. This process of dissolving is known as solvation. 

Slide 33: Important Points 

Have students discuss these questions and review the important concepts presented in this lesson. 

The Science of Water Lab Activities: Teacher Instructions 

Overview 

There are three sets of curricular materials for these labs: 

1. The Science of Water Lab Activities: Teacher Instructions. This document, which includes 
the purpose, safety precautions, and procedures for each lab station, and a complete list of materials 
for each station. 

2. The Science of Water Lab Activities: Student Instructions. The set of directions for students 
is to be printed and posted at each of the appropriate lab stations. They include a statement of 
purpose, safety precautions, materials needed, and procedures for the students to follow. 

3. The Science of Water Lab Activities: Student Worksheet. Each student should be given 
this worksheet onto which they will record their observations. The worksheet also includes questions 
about each lab, designed to stimulate the student to think about how the lab demonstrates concepts 
fundamental to the mechanisms that make water a unique substance. 

Each of the following labs is designed to demonstrate a specific aspect of the unique chemistry of water. 
The lab is set up at multiple stations. Each student or group of students will conduct investigations at 
each station. 

Post the appropriate student instructions at each station for students to follow. 

There needs to be running tap water and paper towels at each lab station. No dangerous substances are 
recommended for this lab. 

The lab stations are: 

Lab Station A: Surface Tension Lab 

Lab Station B: Adhesion/ Cohesion Lab 

Lab Station C: Can You Take the Heat? 

Lab Station D: Liquid at Room Temperature Data Activity 

Lab Station E: Now You See It, Now You Don't, A Dissolving Lab 

Lab Station F: Predict a New World! Inquiry Activity 

Materials 

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A complete list of materials can be found at the end of the set of teacher instructions. 

Time Duration 

Although the set of laboratory experiences is designed to occupy an entire class period, each lab will vary 
in the time that it takes to complete. If time is short, you may have students share their data with each 
other at the end of the class period. Also Lab Stations D and F are paper and pencil labs. You may want 
to assign these to students as homework or as a warm-up rather than as a separate lab station. 

Lab Station A: Surface Tension Lab 

Purpose 

The purpose of this lab is to investigate the property of the surface tension of water. This lab will look at 
the way that water sticks to itself to make a rounded shape, the way that water behaves as a "skin" at the 
surface, and a comparison of water's surface tension with two other liquids, oil and soapy water. 

Safety Precautions 

• Wearing goggles is dependent on your school's safety criteria. 

• Caution needs to be exercised around hot plates and the alcohol burner. 

• Caution needs to be exercised around hot water and hot glassware. 

• Do not eat or drink anything in the lab. 

• Do not wear open-toed sandals in the lab. 

• Wear long hair tied back to prevent touching the substances at the lab stations. 

Materials 

• 3 pennies 

• Available water 

• Small containers of water, oil, and soapy water 

• A dropper for each of the containers 

• A square, about 4" x 4", of wax paper 

Procedures 

Counting Drops on a Penny 

1. Check to make sure all of the materials needed are at your lab station. 

2. Using a dropper bottle containing only water, count the number of drops of water that you can 
balance on top of a penny. When the water falls off of the penny, record the number of drops. Wipe 
the water off of the penny. 

3. Repeat this procedure of counting and recording drops with oil and then with the soapy water. 

Comparing the Shape of a Drop 

1. Drop a small sample of each of the liquids — water, oil, and soapy water — on the wax paper. Draw 
the shape and label the shape of the drops made by each of the liquids on your worksheet. Wipe off 
the wax paper. 

2. Answer the questions on your worksheet. 

Lab Station B: Adhesion/Cohesion Lab 
Purpose 

The purpose of this lab is to investigate the property of cohesion and adhesion of water. 

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• Cohesion is the molecular attraction exerted between molecules that are the same, such as water 
molecules. 

• Adhesion is the molecular attraction exerted between unlike substances in contact. 

Cohesion causes water to form drops, surface tension causes them to be nearly spherical, and adhesion 
keeps the drops in place (http://en.wikipedia.org/wiki/Adhesion). 

This lab will work with capillary tubing of various diameters to see the rate at which water is able to 
"climb" up the tubes. This is very similar to the way that water enters a plant and travels upward in the 
small tubes throughout the plant's body. The "stickiness" of the water molecule allows the water to cling 
to the surface of the inside of the tubes. 

You will see how the diameter of the tube correlates with the rate of traveling up the tube by measuring 
how high the dye-colored water column is at the end of the time intervals. 

Safety Precautions 

. COOL GLASSWARE FOR A FEW MINUTES BEFORE PUTTING INTO THE COOLING BATH 
OR THE GLASSWARE WILL BREAK. 

• Wearing goggles is dependent on your school's safety criterion. 

• Do not eat or drink anything in the lab. 

• Do not wear open-toed sandals in the lab. 

• Wear long hair tied back. 

Materials 

• 4 pieces of capillary tubing of varying small sized diameters (no greater than 7 mm in diameter), 
8-24 inches in length 

• Metric ruler 

• Pan of dyed (with food coloring) water into which to set the capillary tubing 

• Clamps on ring stands to stabilize the tubing so that it remains upright in a straight position 

Procedures 

1. Check to make sure all of the materials needed are at your lab station. 

2. Set the capillary tubing into the dye-colored water from the largest diameter tubing to the smallest. 
Make certain they are all upright and secure. 

3. Record the height of each of the tubes in the table on your worksheet every 2 minutes. 

4. After 10 minutes, release the capillary tubing, wrap the tubing in paper towels, and deposit them in 
an area designated by your teacher. 

5. Answer the questions about this experiment on your lab sheet. 

Teacher Notes 

Try to obtain five different diameters of tubing. These are available through many different suppliers. 

Lab Station C: Can You Take the Heat? 

Purpose 

The purpose of this lab is to investigate the heat capacity of water. You will measure the temperature of 
water (specific heat of water is 4.19 kJ/kg.K) and vegetable oil (specific heat of vegetable oil is 1.67 kJ/kg.K) 
over equal intervals of time, and will record your data and findings on your lab sheet. 

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Specific heat is the amount of energy required to raise 1.0 gram of a substance 1.0°C. 
Safety Precautions 

• Cool hot glassware slowly. Wait a few minutes before placing in cold water or the glass will break. 

• Wearing goggles is dependent on your school's safety criterion. 

• Do not eat or drink anything in the lab. 

• Do not wear open-toed sandals in the lab. 

• Wear long hair tied back. 

• Use caution when working with fire or heat. Do not touch hot glassware. 

Materials 

Assemble two Erlenmeyer flasks or beakers, each containing one of the liquids, with a thermometer held 
by a thermometer clamp that is to be inserted about midway into the liquid. 

• 2 equal amounts, about 100 - mL, of water and vegetable oil 

• 2 250 - mL Erlenmeyer flasks or 2 250 - mL beakers 

• 2 thermometers 

• 2 Bunsen burners or 1-2 hot plates 

• 2 ring stands: each ring stand will have a clamp to hold the thermometer. Use a screen if using a 
Bunsen burner rather than hot plate(s). 

• Cold water bath for cooling the Erlenmeyer flasks or beakers 

Procedures 

1. Set the cooled flasks containing their solutions on the ring stands or hot plate. 

2. Take the initial temperature reading of each of the liquids. 

3. Turn on the hot plate to a medium temperature, or, if using Bunsen burners instead, light them, 
adjusting the flame of each to the same level. 

4. Record the temperature of the liquid in each flask every 2 minutes until 4 minutes after each liquid 
boils. Record the temperature in the table on your lab sheet. 

5. After recording the final temperatures, move the Erlenmeyer flasks or beakers with tongs or a heat- 
resistant set of gloves into the cooling bath. Add small amounts of ice as needed to keep the water 
temperature cold. 

DO NOT THRUST HOT GLASSWARE DIRECTLY INTO ICY WATER BEFORE COOL- 
ING BECAUSE THE GLASS WILL BREAK! 

6. Answer the questions about this experiment on your lab sheet. 

Lab Station D: Liquid at Room Temperature Data Activity 

Purpose 

The purpose of this activity is to discover how unusual it is, based on a substance's molecular weight, that 
water is a liquid at room temperature. 

Safety Precautions 

None are needed, since this is a paper and pencil activity. 
Materials 

• Water is Weird! Data Table 

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• Lab worksheet for recording trends 

Procedures 

Data Table 1 shows the physical properties of a variety of substances. This table is typical of one that 
a chemist would examine to look for trends in the data. For instance, is there any correlation with the 
color of the substance and its state of matter? Is there any correlation between the state-of-matter of a 
substance and its density? How does water compare to other substances? 

1. Examine the data table. Look for relationships between the physical properties of some of these 
substances. 

2. Discuss the trends with your lab partner. Record your thoughts on your lab worksheet. 

3. Answer the questions about this experiment on your lab worksheet. 

Teacher Notes 

If you are short of time, this activity can be done as homework or as a warm-up assignment. If you need 
extra lab station space, this activity can be conducted at the students' desks. 

Water is Weird! Data Analysis Activity 

Water is Weird! How Do We Know? 

We have been discussing the many ways that water is weird. Water seems pretty common to us. How do 
we know that it is unusual? Let's compare water to some other substances and see what we can find, using 
the data table below. 

Record the trends that you notice on your lab worksheet. 

Table 3.16: Physical Properties of Some Substances 



Substance 


Formula 


Molar 


State 


of 


Color 


Specific 


Density of Boiling 






mass, 


matter 






Heat 


gas, liquid, Temper- 






grams 


at nor- 
mal room 
conditions 




J/gK 


or solid ature, 
°C 


Water 


H 2 


18.0 


liquid 




colorless 


4.19 


0.997 g/cm 3 100 


Methane 


CH 4 


16.0 


gas 




colorless 




0.423 -162 g/cmi61.5 


Ammonia 


NH 3 


17.0 


gas 




colorless 




0.701.308 g/L-33 


Propane 


CsH$ 


44.1 


gas 




colorless 




0.493 25 g/cm-42.1 


Oxygen 


o 2 


32.0 


gas 




colorless 


0.92 


1.308 g/L -182.9 


Carbon 


co 2 


44.0 


gas 




colorless 




1.799 g/L -78.5 


dioxide 
















Bromine 


Br 2 


159.8 


liquid 




red 


0.47 


4.04 58.8 


Lithium 


Li 


6.94 


solid 




silvery, 

white 

metal 


3.58 


0.534 g/cm 3 1342 


Magnesium 


Mg 


24.3 


solid 




silvery, 

white 

metal 


1.02 


1.74 g/cm 3 1090 



Lab Station E: Now You See It, Now You Don't A Dissolving Lab 

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Purpose 

The purpose of this activity is to introduce the idea that different types of liquids may dissolve different 
substances. 

Safety Precautions 

• Wearing goggles is dependent on your school's safety criterion. 

• Do not eat or drink anything in the lab. 

• Do not wear open-toed shoes. 

• Tie long hair back. 

Materials 

• 6 plastic cups 

• 6 plastic spoons 

• Water 
. Oil 

• Granulated salt 

• Granulated sugar 

• Iodine crystals 

Procedures 

1. Fill 3 plastic cups 1/3 to 1/2 full with water. 

2. Fill 3 plastic cups 1/3 to 1/2 full with oil. 

3. Put about a half-teaspoon of salt into the water in one cup and another half-teaspoon of salt into 
the oil in one cup. 

4. Stir each for about 20 seconds or until dissolved. 

5. Record your observations in the table on your lab sheet. 

6. Repeat this procedure with sugar. 

7. Repeat this procedure using iodine crystals BUT only drop 2 or 3 crystals into the water and into 
the oil. 

8. Record your observations and answer the questions about this experiment on your lab sheet. 

Lab Station F: Predict a New World! Inquiry Activity 

Purpose 

We all know that ice floats; we take it for granted. However, in nature, the solid form of a substance 
being less dense than the liquid form is extraordinary. What we don't know or think about much is how 
our world would be affected if ice did not float in water. This "thought" activity explores the worldly 
implications if ice had a greater density than water. 

Safety Precautions 

None are required because this is a paper and pencil activity. 
Materials 

• Place a fish bowl with some fish and live plants at this station 
Procedures 

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1. Read the following. Look at the fish bowl. Think. Write your thoughts on your lab worksheet. 

Assume that there will be one change in the way that nature behaves: On the day after tomorrow, 
worldwide, ice (the solid form of water) will now become denser than water, rather than its current state, 
which is less dense. 

What will be the impact of this change? 




Figure 3.58: Beautiful lake in early winter. [1] 

2. Discuss this with your lab partner. 

3. Answer the questions about this experiment on your lab worksheet. 
Reference 

• http : //snow . reports . co . nz/snow_ida_800 . jpg 

Teacher Notes 

This assignment can be homework assigned before this lesson, if there is not sufficient time to do this as a 
lab activity, or if you prefer. 

Materials List 

• 3 pennies 

• Available water 

• Small containers of water, oil, and soapy water, and a dropper for each 

• A square, about 4" x 4", of wax paper 

• Hot plate 

• Thermometer 

• Ice water (without the ice) 

• 4 pieces of 8 - 24 inches of capillary tubing of varying small sized dimensions, no greater than 7 mm 

• Metric ruler 

• Pan of dyed (with food coloring) water into which to set the capillary tubing 

• Clamps on stands that will stabilize the tubing to remain upright in a straight position 

• 2 equal amounts, about 100 - mL, of water and vegetable oil 

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2 250 - mL Erlenmeyer flasks or beakers 

2 thermometers 

2 Bunsen burners or a hot plate 

2 ring stands, with screens if needed, to hold Erlenmeyer flasks or beakers 

2 additional clamps to hold the thermometers in place 

Cold water bath for cooling the Erlenmeyer flasks 

6 plastic cups 

6 plastic spoons 

Water at room temperature 

Oil at room temperature 

Granulated salt 

Granulated sugar 

Iodine crystals 

A timer with a second hand 

Glassware tongs or heat resistant mitts 

100 - mL graduated cylinder 



The Science of Water: Quiz Answer Key 

Write down your ideas about each question below. 

1. Why does all bonding occur between atoms, ions, and molecules? 
All bonding occurs because of the attraction of opposite charges. 

2. Draw a water molecule. Label the atoms that make up the water molecule with their chemical symbol. 
If there is an electrical charge or a partial electrical charge on any of the atoms, indicate that by writing 
the symbols on the atoms: 



+ = positive charge 

d + = partial positive charge 



- = negative charge 

S~ = partial negative charge 



( <M 



Figure 3.59 

3. Explain the term "polar" molecule. 

A polar molecule has a more positive end and a more negative end. These can be permanent or they can 
be temporary. 



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450 



4. Why does water have an increased surface tension compared to most other liquids? 

A water molecule has a greater surface tension relative to other liquids because the water molecules are 
more strongly attracted to the other water molecules surrounding them on all sides, as compared with the 
water molecules at the surface, which are surrounded by air (mostly nitrogen and oxygen gases). Water is 
not attracted to air molecules. 

5. What is "hydrogen bonding"? What makes these bonds unique? 

Hydrogen bonding is the bonding that occurs between adjacent water molecules. (Alhough our focus is on 
water, there are other molecules that exhibit hydrogen bonding as well as water.) The positive end of one 
water molecule is attracted to the negative end of the next water molecule. This is why water is a liquid 
at room temperature. A definition of hydrogen bonding is: The attraction of one end of a small, highly 
electronegative nonmetal atom in a molecule to the hydrogen end, more electropositive, end of an adjacent 
molecule. 

6. a. Define or describe "specific heat." 

Specific heat is the amount of energy required to raise 1.0 gram of a substance 1.0°C. 

b. How does water's specific heat have an impact on our climate? 

The temperature of the air near large bodies of water is more moderate than the temperature of air that is 
not near a large body of water. For instance, for cities bordering the ocean, the ocean absorbs heat during 
the day, making air temperatures cooler than they would be inland. At night, the ocean slowly releases 
the heat absorbed during the day, making the air temperatures warmer than they are inland. 

7. Is water's specific heat, compared to other liquids: 
High Kl or Average □ or Low □ 

8. Are water's melting and boiling temperatures, compared to other liquids: 
High H or Average □ or Low □ 

9. a. What happens to the temperature of the water in a pot on a heated stove as it continues to boil? 
The temperature of the water stays at 100°C during boiling. 

b. Explain what the energy is being used for that is heating the water at the boiling temperature. 

The heat energy being continually added to a pot of water during boiling is used to break the bonds 
of attraction (hydrogen bonding) between water molecules, so that each individual water molecule may 
change from the liquid phase to the gas phase. 

10. Explain how a spider can walk on water. 

The surface tension of the water is greater than the pull of the gravity on the spider's little feet. 

11. Fill out the following table: Name and explain five of water's unique properties, and provide an example 
of the phenomenon in nature caused by each of these properties. 

Table 3.17: 



Property of Water 



Explanation of Property 



Phenomenon Property Causes 



High boiling temperature 



High surface tension 



It takes a relatively large amount 
of energy to boil water compared 
with other small nonmetal liq- 
uids. 

The surface of water acts like a 
"skin." 



Water at sea level must reach 
100°C before it will boil. 



Spiders can walk on water. 



451 



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Table 3.17: (continued) 



Property of Water 



Explanation of Property 



Phenomenon Property Causes 



High specific heat 

Solid is less dense than liquid 
Universal solvent 



Water absorbs a relatively large 
amount of energy to raise its tem- 
perature VC. 

Water expands in volume when 
frozen. 

Water dissolves positive and neg- 
atively charged particles. 



Climate near large bodies of wa- 
ter is moderate compared with 
climate further away from large 
bodies of water. 
Ice floats rather than sinks. 

Water is not found "pure" in na- 
ture because it dissolves so much 
of what it comes into contact 
with. 



Reflecting on the Guiding Questions: Teacher Instructions 

You may want to have your students keep these in a folder to use at the end of the unit, or collect them 
to see how your students' thinking is progressing. 

Think about the activity you just completed. What did you learn that will help you answer the guiding 
questions? Jot down notes in the spaces below. 

1. Why are water's unique properties so important for life as we know it? 
What I learned in these activities: 

What I still want to know: 

2. How do we make water safe to drink? 
What I learned in these activities: 
What I still want to know: 

3. How can nanotechnology help provide unique solutions to the water shortage? 
What I learned in these activities: 

What I still want to know: 

4. Can we solve our global water shortage problems? Why or why not? 
What I learned in these activities: 

What I still want to know: 

Nanofiltration 

Contents 



Nanofiltration: Teacher Lesson Plan 

Nanofiltration: Teacher Reading 

Nanofiltration: PowerPoint with Teacher Notes 

Which Method is Best? Answer Key 

Comparing Nanofilters to Conventional Filters Lab Activity: Teacher Instructions 

Cleaning Jarny's Water: Teacher Instructions & Rubric 



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452 



• Reflecting on the Guiding Questions: Teacher Instructions 

Teacher Lesson Plan 

Orientation 

As a dynamic, evolving area of science, nanotechnology can provide an exciting learning opportunity for 
students, offering them the opportunity to learn about current science and technology innovations that 
may improve our world. The use of nanofiltration for cleaning water is one such innovation. Scientists are 
working to develop newer, cheaper and more effective membrane technologies to clean water. Much of the 
current work has focused on new designs of nanofilters, and nanofiltration systems are currently deployed 
in a few metropolitan areas. 

Learning about nanofiltration also reinforces important fundamental chemistry concepts that are sometimes 
difficult for students to grasp. Students must understand differences in solution types to understand how 
different filtration systems work on a small scale. The topic of nanofiltration also has the potential to help 
students see interdisciplinary connections between biology, chemistry, and engineering. 

The lessons in the Fine Filters unit focus conceptually on the role of membrane technology for filtering 
water. The presentation, notes, activities and readings focus on key aspects of filtration such as underlying 
technologies, particle filtration sizes, and applications. 

• The Nanofiltration Teacher and Student Readings provide background on how nanofiltration works. 
The teacher reading is recommended prior to presenting the Nanofiltration PowerPoint slides and 
other activities. 

• The Nanofiltration PowerPoint slide set provides a brief introduction to the different types of filtration 
and how they work, with emphasis on nanofiltration methods. 

• The Which Method is Best exercise is a worksheet activity that allows students to explore some of 
the basic ideas of filtration, such as membranes and particle size, and prepares them for the more 
involved lab activity. 

• The Comparing Nanofilters to Conventional Filters lab activity gives students a hands-on opportunity 
to better understand two types of filtration. 

• The Cleaning Jarny's Water exercise allows students to explore ideas of filtration in a real-world 
application. 

• The New Nano-Membranes Reading introduces students to current research in creating nanotechnol- 
ogy membranes 

• The Reflecting on the Guiding Questions Worksheet asks students to connect their learning from the 
activities in the lesson to the driving questions of the unit. 

Essential Questions (EQ) 

What essential question(s) will guide this unit and focus teaching and learning? 

(Numbers correspond to learning goals overview document) 

2. How do we make water safe to drink? 

3. How can nanotechnology help provide unique solutions to the water shortage? 
Enduring Understandings (EU) 

Students will understand: 

(Numbers correspond to learning goals overview document) 

3. Pollutants can be separated from water using a variety of filtration methods. The smaller the particle 

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that is to be separated from a solution, the smaller the required pore size of the filter and the higher the 
cost of the process. 

4. Innovations using nanotechnology to create a new generation of membranes for water filtration are 
designed to solve some critical problems in a cost-effective way that allows for widespread use. 

Key Knowledge and Skills (KKS) 

Students will be able to: 

(Numbers correspond to learning goals overview document) 

2. Describe different types of filtration in terms of the pore size of the filter, substances it can separate, 
and cost of use. 

3. Use laboratory procedures to compare the relative effectiveness of different filtration methods on particle 
separation. 

Table 3.18: 



Day 



Activity 



Time 



Materials 



Day 1 (50 min) 



Homework: Nanofiltra- 20 min 
tion: Student Reading 

Show the Nanofiltration 30 min 
PowerPoint slides, using 
the teacher's notes to 
start class discussion. 



Photocopies of Nanofil- 
tration: Student Read- 
ing 

Nanofiltration Power- 
Point Slides &; Teacher 
Notes 
Computer and projector 



Hand out the Which 
Method is Best? Stu- 
dent Worksheet and 
The Filtration Spec- 
trum: Student Handout 
and have students work 
in small groups to 
answer the questions. 



10 min 



Photocopies of Which 
Method is Best? Stu- 
dent Worksheet 
Photocopies of The Fil- 
tration Spectrum: Stu- 
dent Handout 



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454 



Table 3.18: (continued) 



Day 



Activity 



Time 



Materials 



Return to whole class 
discussion and have 
students share their 
ideas on which types 
of membrane can 
filter which type of 
particles. You may 
want to have different 
students each draw a 
particular membrane 
and related filtrated 
particles to help drive 
class discussion. 
This activity is a prepa- 
ration exercise for the 
lab that will take place 
on day 2 of this les- 
son. Pre-read the lab 
and give students an in- 
dication of what to ex- 
pect during the next 
class session. 



10 min 



Comparing Nanofilters 
to Conventional Filters 
Lab Activity: Teacher 
Instructions 



Day 2 (50 min) 



Day 3 (50 min) 



Homework: Read the 25 min 
Comparing Nanofilters 
to Conventional Filter 
Lab Activity: Student 
Instructions in prepara- 
tion for the next class. 
Have students work in 50 min 
pairs or small groups on 
the Comparing Nanofil- 
ters to Conventional 
Filters Lab Activity. 
Each student should 
complete their own 
Student Worksheet, 
although they may con- 
sult with other group 
members or the teacher. 
Homework: New Nano- 15 min 
Membranes: Student 
Reading 

Have students work on 25 min 
the Cleaning Jarny's 
Water activity in small 
groups. 



Photocopies of the 
Comparing Nanofilters 
to Conventional Filters 
Lab Activity: Student 
Instructions 

Photocopies of the 
Comparing Nanofilters 
to Conventional Filters 
Lab Activity: Student 
Worksheet 



Photocopies of New 
Nano- Membranes: 
Student Reading 
Photocopies of Cleaning 
Jarny's Water: Student 
Instructions & Report 



455 



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Table 3.18: (continued) 



Day 



Activity 



Time 



Materials 



Have students dis- 10 min 
cuss the New Nano- 
Membranes: Student 
Reading in small 
groups. 

Have students work in- 10 min 
dividually or in small 
groups to fill out the 
Reflecting on the Guid- 
ing Questions: Student 
Worksheet. 

Discuss the Essential 5 min 
Questions and the 
group's collective abil- 
ity to answer them 
based on the work done 
in the unit and answer 
any remaining student 
questions. 



Photocopies of the New 
Nano-Membranes: Stu- 
dent Reading 



Photocopies of Reflect- 
ing on the Guiding 
Questions: Student 

Worksheet 



Teacher Reading 

How is Water Cleaned? 

Water cleansing is complex. There are many methods for making water safe to drink. In addition, new 
technologies are being researched and patented at a relatively rapid rate. Typically, water is cleaned 
through multi-step processes that balance efficacy (i.e. contaminant removal) with cost-effectiveness. 

Non-Filtration Techniques 

While filtration is the main technique used to clean water, there are several common methods of cleaning 
water that are used independently and/or in addition to filtration. 

• Distillation processes use heat to evaporate water. The gas then condenses, leaving all impurities 
behind except those (some pesticides and fertilizers) with boiling points lower than water that get 
evaporated and then condensed along with the water. This method is expensive. It also leaves the 
water tasteless, and without minerals. 

• Ion exchange methods work by passing ion-containing water through resin beads, which exchange 
OH and H + ions for the unwanted ions. 

• UV methods use ultraviolet light as a germicide to kill bacteria and other microorganisms in water. 
These methods do not remove particulates or ions. 

• Chemical- based methods are used to cause flocculation (the formation of small clumps of particles, 
making them easier to remove), precipitation or oxidation of particles. 

Water Filtration 

Filtration is the process of passing a fluid through a porous object or objects (for example cheesecloth or 
sand) in order to separate out matter in suspension [1]. Filtration is the primary process used to clean 



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456 



water for human use. 

Some Vocabulary Clarification 

Many words with similar meanings are used to describe parts of the filtration process. These words are 
used interchangeably in the water filtration literature. These words and their meanings are illustrated in 
Figure 1. 

Affluent: a solution 

containing particles to be ~* Flow 

filtered ^~"-~-^- . 

■ Di.'.olv«l Orgies * o "* " O^V* * 

D Dbxlwd Ir^onK:. ° * < °. £> t> o ^ ,? «%<? D 0< 

o Mi.. , _ 5 g^ 0> ; u ; g^ - ♦& 

A Bcdvia < » o .*o*Oco4„t? ♦": A Filter 






EffluentTiltiate.Permeate: 
the fliud that has passed 
through the filter 




Figure 3.60: Particles passing through a carbon filter [2]. 



Kinds of Filtration 



The following is a list of commonly used filtration types. All of them use membrane technologies, except 
for carbon filtration which uses a collection of small grains. Each of these filter types are expanded upon 
in Table 1, including examples of particle types they can remove and diagrams of the filters. A simplified 
version of Table 1 is also provided as a student handout (Types of Filtration Systems and their Traits: 
Student Handout). 

• Carbon filtration traps larger organic particles on the surface of small carbon grains. Different 
types of filters are capable of trapping different substances. 

• Microfiltration methods employ depth, screen or surface membranes: 

— Depth filters consist of matted fibers that retain particles as they pass through the filter. 
About 98% of the particles passing through this type of microfilter are retained, protecting 
finer-scale membranes farther down the chain. Depth microfilters are considered good prefilters 
for this reason. 

— Surface filters are multilayered structures that remove 99.99% of suspended solids, and are 
also used as prefilters. 

— Screen filters are microporous membranes that trap particles based on the specific pore size 
of the membrane. 

• Ultrafiltration methods employ a thin, yet tough, membrane with a very small pore size. 

• Nanofiltration methods focus on pore size, charge (repulsion), and shape characteristics of the 
membrane. A moderate amount of pressure is required for nanofilters to operate effectively. 

• Reverse osmosis methods use a selectively-permeable membrane to separate water from dissolved 
substances. Relatively high pressure is required to make water flow against normal osmotic pressure. 

Filtration Trade-offs 

Generally, the smaller the filter, the more pressure is needed to push the water through it. Greater pressure 
means a greater cost, and so filters that remove very small particles are the most expensive to use. To 
be cost-effective, filtration is usually done as a multi-step process. Bigger contaminants are first removed 
using large-pore (and thus less expensive) filters, then filters with decreasing pore sizes are used to remove 
smaller and smaller particles. Using a sequence of filters also keeps the small-pore filters from getting 

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clogged up with the large contaminants. This clogging is called "fouling." Filters must be cleaned regularly 
to remain usable 

State of the Art? 

While constantly improving, our current water purification technology is inadequate to meet the current or 
the projected needs of the world's population for clean drinking water. New nanofilters are being explored 
with much anticipation and excitement for their potential to address the global water crisis. 

References 

(Accessed December 2007.) 

• http://www.m-w.com/dictionary/filter 

• Adapted from http://www.freedrinkingwater.com/water-education/quality-waterfiltration-method. 
htm 

• Adapted from http://www.homecents.com/images/h2o-imgs/nano_f_l.gif 

• Adapted from reverse_osmosis.jpg http : //www . zenon . com/image/resources/glossary/reverse_ 
osmosis/ reverse_osmosis.jpg 

• http://www.nesc.wvu.edu/ndwc/ 



Table 3.19: Types of Filtration Systems and their Traits 



Type of Filtra- Max Particle Characterization Example Parti- Disadvantages 
tion Size (meters) cles 



Carbon Fil- Above 10~ 6 
tration (CF) 



Large organic Removes bad No effect on 

particles are tastes and total dissolved 

trapped on odors (organic solids, hard- 

the surface of matter) and ness, or heavy 

small carbon chlorine metals. 



grains. 

Used in com- 
bination with 
other filtration 
processes. 



Varies widely 



Diagram 



■ • .-" •..■' • 



'.-] 



Microfiltration 10 5 to 10 7 
(MF) 



Removal based 
on relatively 
large pore 

size, retains 
contaminants 
on surface. 
Very low wa- 
ter pressure 
needed. 

Often used as a 
pre-filter. 



Sand, silt, 

clays, Giar- 
dia lamblia, 
Cryptospoid- 
ium, cysts, 

algae and some 
bacteria 



Removes little 
or no organic 
matter. 

Does not re- 
move viruses. 




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458 



Table 3.19: (continued) 



Type of Filtra- Max Particle Characterization Example Parti- Disadvantages Diagram 
tion Size (meters) cles 



Ultrafiltration 10 7 to 10 8 
(UF) 



Nanofiltration 10 8 to 10 10 
(NF) 



Removal based 
on smaller pore 
size, retains 
contaminants 
on surface. 
Low wa- 

ter pressure 
needed. 

Removal based 
on very small 
pore size and 
shape and 

charge char- 
acteristics of 
membrane. 
Moderate pres- 
sure needed. 



Suspended or- 
ganic solids 
Partial removal 
of bacteria 
Most viruses 
removed 



Suspended 
solids 
Bacteria 
Viruses 

Some multiva- 
lent ions 



Most problems 
are with foul- 
ing. 

Cannot remove 
iron or man- 
ganese ions 
(multivalent 
ions). 

Currently most 
are susceptible 
to high fouling. 
Cost is rel- 
atively high 
(currently) . 



_ ' 3 ' j TT^'. y^^ * '.y^'.'yv,' 



Tit [TH 



\-} 




Reverse Os- 
mosis (RO) 



10 -9 to 10~ n 



High pressure 
process that 
pushes water 
against the 
concentration 
gradient 
Different 
membranes 
have different 
pore sizes 

and different 
characteristics. 



Suspended 
solids 
Bacteria 
Viruses 

Most multiva- 
lent ions 
Monovalent 
ions 



Membranes are 
prone to foul- 
ing. 
Cost is high. 




Note: Relative Pressure needed for operation: RO > NF > UF > MF 

Relative Cost: RO > NF > UF > MF [5] 

Nanofiltration 



459 



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Environmental scientists and engineers are creating nanomembranes to filter contaminants from water 
cheaply and effectively 

Water Filtration Methods 

There are simple and cheap ways to filter contaminants out of water 
Sand, Gravel, and Charcoal Filtration 



Fittrtd 
Outflow 




P««for»t»d 



Sand and gravel filtration 



Figure 3.61 



• Pouring water through sand, gravel, or charcoal are simple and inexpensive methods of cleaning water 
Small Contaminants Pass Through 

• Sand, gravel, and charcoal don't filter out some contaminants, like 

— bacteria 

— viruses 

— industrial pollutants 

— agricultural pollutants 

— salt 



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Figure 3.62 



461 



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Question 

How Can We Trap Smaller Contaminants? 




Figure 3.63 



Membrane Filter Technology I 



A membrane is a thin material that has pores (holes) of a specific size 

Membranes trap larger particles that won't fit through the pores of the membrane, letting water and 

other smaller substances through to the other side 



£i*^jmitfi<r 



• «o 



• * 



Figure 3.64 
Membrane Filter Technology II 

• There are four general categories of membrane filtration systems 
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Microfiltration 
Ultrafiltration 
Nanofiltration 
Reverse Osmosis 



Table 3.20: Membrane Filter Technology III 



Filter type 



Symbol 



Pore Size, //m 



Operating Pres- Types of Materials 
sure, psi Removed 



Microfilter MF 



Ultrafilter UF 



Nanofilter NF 



Reverse Osmosis RO 



1.0-0.01 



0.01-0.001 



0.001 - 0.0001 



< 0.0001 



<30 



20 - 100 



50 - 300 



225-1,000 



Clay, bacteria, 

large viruses, 

suspended solids 
Viruses, proteins, 
starches, colloids, 
silica, organics, 
dye, fat 

Sugar, pesti- 

cides, herbicides, 
divalent anions 
Monovalent salts 



(Source: http : //web . evs . anl . gov/pwmis/techdesc/membrane/index . cf m) 
Microfiltration 

• Typical pore size: 0.1 microns (10~ 7 m) 

• Very low pressure 

• Removes bacteria, some large viruses 

• Does not filter 

— small viruses, protein molecules, sugar, and salts 
Ultrafiltration 

• Typical pore size: 0.01 microns (10 -8 m) 

• Moderately low pressure 

• Removes viruses, protein, and other organic molecules 

• Does not filter inoic particles like 

— lead, iron, chloride ions; nitrates, nitrites; other charged particles 
Nanofiltration 

• Typical pore size: 0.001 micron (10 -9 m) 

• Moderate pressure 

• Removes toxic or unwanted bivalent ions (ions with 2 or more charges), such as 

— Lead 

— Iron 

— Nickel 



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Microfiltration water plant, Petrolia, PA 




A microfilter membrane 



Figure 3.65 



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An ultrafiltration plant in 
Jachenhausen, Germany 

Figure 3.66 



465 



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Nanofiltration water cleaning 
serving Mery-sur-Oise, a suburb 
of Paris, France 



Figure 3.67 



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466 



— Mercury (II) 
Reverse Osmosis (RO) 




Reverse osmosis (or desalination) 
water treatment plants, like this one, 
are often located close to the ocean 

Figure 3.68 



• Typical pore size: 0.0001 micron (10~ 10 m) 

• Very high pressure 

• Only economically feasible large scale method to remove salt from water 

— Salty water cannot support life 

— People can't drink it and plants can't use it to grow 

How RO Works 

• Osmosis is a natural process that moves water across a semipermeable membrane, from an area of 
greater concentration to an area of lesser concentration until the concentrations are equal 

• To move water from a more concentrated area to a less concentrated area requires high pressure to 
push the water in the opposite direction that it flows naturally 

Question 

If RO Can Get Everything Out That Would Make Water Undrinkable, Why Not Just Use 
RO Membranes by Themselves? 

RO is Not for Everything! 



467 



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-a h^ 

• a _ ° ■ # 

* Wdcnnofaafc 

^t O # O^ci MibMaiKCs diMolve* 

Osmosis 






Reverse Osmosis 

Figure 3.69 




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Fouling of RO pores 




O O O v 



e oo o 




Pores clogged with 
large objects 

Figure 3.70 



• High pressure is required to push the water through the smallest pores 

— RO is the most $$$ filtration system 

• Because pores are so small, big particles can clog them (called fouling) 

— This makes the filtering membrane unusable 

Question 

How Can We Keep Large Particles from Fouling Membranes with Small Holes? 

A Series of Filtrations Increases Efficiency 

• Filters can be sequenced from large to small pore size to decrease fouling 

— They must still be cleaned regularly to remain usable 

Water Filtration Chart 
Nanofiltration vs. Reverse Osmosis 

• Using RO to get rid of very small particles is very expensive 

— Could we do it more cheaply? 

• Nanofiltration requires much less pressure than reverse osmosis 

— Less pressure means lower operating costs! 

Advantages of Nanofiltration 

• Nanofilters are close in size to RO filters, but cost much less to run 

469 



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Microfiltration 



Nanofiltration 



Ultrafiltration 

I 



Reverse Osmosis 



I 







.* 


E COl st 


Viruses 


» Ions 


-*- 


Oil 


Proteins 


- 


o 


WacroTiclecLtM 




Compounds 


o 


Colloids 






a 


Suspended 

Particles 




Figure 3.71 




Figure 3.72 



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470 



S450.W 

S44IUJH' 

S^J.I'U- 

«on.r«n 



UWM 

Slf'J.l'U 

ftMJtf-N 

KOJK 
SOJM 



jft 



ErTTr 



U 1 2 J 4 5 6 7 » f Ml 

Flt(rPmsureDrcc(psid) 

What does this chart say 
about the cost of pressure 
used for filtration? 

Figure 3.73 

• And special properties of nanosized particles can be exploited! 

— We can design new nanofilters that catch particles smaller than they would catch based on size 
alone 

• Scientists are exploring a variety of methods to build new nanomembranes with unique properties to 
filter in new and different ways 

New Nanofilters are Unique! 

• Nanomembranes can be uniquely designed in layers with a particular chemistry and specific purpose 

— Insert particles toxic to bacteria 

— Embed tubes that "pull" water through and keep everything else out 

— Signal to self-clean 

New Nanomembranes I 

• Imagine having layers of membranes into which specialized substances are placed to do specific jobs 

— You can put a chemical in the filter that will kill bacteria upon contact! 

New Nanomembranes II 

• Embed "tubes" composed of a type of chemical that strongly attracts ("loves") water 

• Weave into the membrane a type of molecule that can conduct electricity and repel oppositely charged 
particles, but let water through 



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J 



Image of a nanomembrane 



Figure 3.74 




Bact«Ma 



Chemicals toxic to bacteria 
could be implanted in 
nanomembranes 

Figure 3.75 



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i" Wa ter-loving tubes 

iff 





Electricity moving 
through a membrane 

Figure 3.76 



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Representation of an 
electric field above a 
nanopore pushing away 
negative ions 



Figure 3.77 



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474 



1 nm Sized Nanopores Repel Electronegative Objects 

• 1-2 nm sized pores create an electric field over the opening 

— This electric field is negative, and repels negatively charged particles dissolved in water 

— Most pollutants from agriculture, industry, and rivers are negatively charged 

• But water can get through! 
Nanofiltration Summary 

• At the nanoscale, filters can be constructed to have properties designed to serve a particular purpose 

• Scientists and engineers are now experimenting to create membranes that are low-cost yet very 
effective for filtering water to make it drinkable! 

• These inventions may help to solve the global water shortage 

Questions 

• How do you determine what filtration method to use to remove contaminants in a water sample? 

— Consider the size of the contaminants, the relative cost of the filtration methods, and the water 
use 

• What are two benefits that nanomembranes bring to the filtration of water? 

— Consider how they can help to address the world's problem of a scarcity of clean drinking water 

• Describe three ways that current or experimental nanofiltration membranes may be different than 
previous generation membranes 

Teacher Notes 

Overview 

This set of slides provides some general background about the processes of water filtration. Common 
processes involve a sequence of nitrations through different kinds of membranes designed to remove different 
sizes of particles. Water is also often treated chemically, is sometimes irradiated, and even has substances 
added back into the water to improve its flavor. These slides give students a broad background in water 
filtration so that they can appreciate the innovations being explored by scientists and engineers who are 
designing nanomembranes for water filtration. 

Slide 1: Title Slide 

Slide 2: Water Filtration Methods 

Removing contaminants to make water drinkable can be complex. Although the focus of this lesson is on 
membrane filtering technologies, there are simple and cheap methods for removing large contaminants in 
water, such as passing water through gravel, sand, and/or charcoal. 

Slide 3: Sand, Gravel, and Charcoal Filtration 

Students will be working with sand, gravel, and charcoal filtration in their lab activities. These are the 
very simple, inexpensive methods for cleaning large-sized contaminants out of water. 

Slide 4: Small Contaminants Pass Through 

However, sand, gravel, and charcoal filtration methods are not able to remove bacteria, viruses, and 
industrial or agricultural pollutants from water. If a water source has any of these contaminants, other 
filtration or cleaning methods must be used as well to produce safe drinking water. 

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Slide 5: How Can We Trap Smaller Contaminants? (Question Slide) 

Have your students brainstorm ideas about ways to trap small contaminants like bacteria or viruses, which 
are not trapped by sand, gravel, or charcoal filtration. 

Slide 6: Membrane Filter Technology I 

This slide introduces students to the idea of a membrane blocking some (e.g., smaller) substances while 
allowing others to pass through. The basis of most membrane blockage is pore size. The size of the pore 
will determine what substances pass through the membrane and which ones remain on the other side. 

Slide 7: Membrane Filter Technology II 

This slide lists the four common types of membranes used for filtering water for drinking. There are many 
types of filters and methods of cleaning water, but this slide set focuses primarily on membrane technology, 
leading into a discussion of nanomembranes. 

Slide 8: Membrane Filter Technology III 

This is a quick overview that compares the four types of membrane filters on the basis of pore size, operating 
pressure, and type of substances that each of the membranes can remove. Students will look at these in 
more detail during the Cleaning Jarny's Water activity. 

Slide 9: Microfiltration 

The pore diameter of microfiltration membranes is typically in the range of 0.01 to 1.0 micrometers, with a 
typical diameter of 0.1 microns. Thus, microfiltration can be used to filter bacteria and some large viruses 
from water. It cannot filter out smaller contaminants like small viruses, proteins, molecules, sugar, and 
salts. The pressure required to push water through a microfiltration membrane is minimal. This slide 
shows a picture of a microfiltration water treatment plant and a close-up of a microfiltration membrane. 
You can see the pores in this membrane! 

Slide 10: Ultrafiltration 

Ultrafiltration can remove viruses, proteins, and other organic molecules from water using a moderately 
low amount of pressure. Ultrafiltration is an economical choice since not very much pressure is required to 
operate an ultrafiltration water treatment plant. 

This slide would be a good place to point out that ions are charged particles that get dissolved into the 
water from natural and unnatural sources. Water, as a universal solvent, has the potential to dissolve 
small amounts of whatever the water passes over. Nitrates and/or nitrites and phosphates in excess in the 
water can be a sign of agricultural pollutant run-off. 

Increased nitrates and/or phosphates in the water can lead to a series of events that ultimately cause a 
lake to lack sufficient nutrients to support fish life. At first, increased nitrates and phosphates provide 
basic nourishment to plants that will stimulate plant growth. Plant growth leads to an abundance of food 
for animals. Animal populations tend to increase as well when plant growth is surging. But too many 
animals in the water decreases the amount of dissolved oxygen, which is necessary for fish to live. Dead 
fish in the water decompose, providing nutrients for even more algae to grow. These events can lead to 
what is known as eutrophication, or a series of cause and effect events that lead to changing the ecosystem 
of a lake resulting in troubling impacts: decreased biodiversity and changes in the dominant species. This 
concept is not addressed at all within this lesson, but if appropriate, you may want to mention it. 

Slide 11: Nanofiltration 

This slide introduces "traditional" nanofiltration, which, like many of the other filtration technologies, has 
been around for decades. Later slides will talk about some of the new an innovative work occurring in the 
science and engineering of nanofilters. 

Nanofiltration can remove bivalent ions (ions with more than one charge). Several nanofiltration plants 
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have been built worldwide, but they are still relatively uncommon. This membrane technology is typically 
used when there is a limited amount of salt in the water. 

Slide 12: Reverse Osmosis (RO) 

Reverse osmosis (RO) is a membrane technology, about 35 years old, that can separate salt from water. 
RO membranes have essentially remained unchanged in recent decades. Though RO is the only known 
technology currently capable of desalinizing water, the process requires very high pressure, and is the most 
expensive membrane filtering system. Cities located by oceans are often good candidates for cleaning salt 
out of water. 

Slide 13: How RO Works 

As highlighted in the previous slide, reverse osmosis is the most successful and effective method of removing 
salt from water. These illustrations show how osmosis, a natural cellular process, pushes water across cell 
membranes by going in a direction that is more concentrated (and will therefore, be diluted when more 
water is added), until the concentrations are equal on both sides of the membrane. In our bodies, our 
kidneys perform this function. 

Dialysis tubing is a common piece of lab equipment used in high school biology labs to demonstrate osmosis. 
Reverse osmosis goes in the "unnatural" direction, from the side that is more concentrated (without as 
many substances dissolved in the water) through the membrane to the side that is less concentrated. A 
great deal of pressure must be applied to push the water into an area less concentrated. The greater the 
pressure required to move the water through the filtration membrane, the higher it costs to operate the 
filtering system. 

Slide 14: If RO Can Get Everything Out That Would Make Water Undrinkable, Why Not 
Just Use RO Membranes by Themselves? (Question Slide) 

Have your students brainstorm about why RO by itself might not be the best solution. Ideas that they 
may entertain include: high cost (since RO requires high pressure), plugging of the RO membrane from 
large particles, and that not all water has salt in it that needs to be removed (e.g., fresh or lake water) so 
RO may be overkill in some cases. 

Slide 15: RO is Not for Everything! 

This slide points out that high pressure, high cost, and fouling are associated with using RO membranes. 
More pressure requires more energy use. Designing and maintaining (cleaning) a very small pore size is 
also very costly. You might point out that in the image, a few of the particles are blocking some of the 
pores. 

Slide 16: How Can We Keep Large Particles from Fouling Membranes with Small Holes? 
(Question Slide) 

Read the question posed on the slide out loud, and have your students brainstorm answers. Fouling can 
occur with every membrane filter system, when the pores of the filter become plugged with particulate 
matter that is larger than the pores. 

The next two slides address this question, showing how filtering technology can occur in a step- wise fashion 
to optimize the more expensive filtration systems. 

Slide 17: A Series of Filtrations Increases Efficiency 

This slide illustrates the consecutive removal of increasingly small contaminants using a series of filters. 
It is less expensive to remove larger-sized contaminants with gravel, sand, or charcoal, and to use a series 
of increasingly smaller pore-sized membranes to remove increasingly smaller particles than to remove all 
sizes of particles with the membranes with the smallest sized pores. The filters would quickly foul and be 
in frequent need of cleaning. Using nanofiltration or RO to remove only small particles optimizes these 
expensive membranes for those sized particles that can only be filtered out of water by them. 

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Slide 18: Water Filtration Chart 

This is a picture of the Filtration Spectrum: Student Handout that correlates the types of particles with 
their size, type of filter required to remove the particle from the water, and the type of microscope needed 
to view these sizes of particles. It illustrates the filtration methods that have been discussed so far. You 
might use the chart to quickly review the various methods that have been discussed. 

Slide 19: Nanofiltration vs. Reverse Osmosis 

This slide points out that RO can get rid of small particles, but it is expensive. Can we remove small 
particles more cheaply? 

This graph demonstrates the correlation between the amount of pressure required and the cost of the water 
filtration system. The more pressure, the more energy is required, and the higher the operating cost. 

Slide 20: Advantages of Nanofiltration 

The pores in nanomembranes are close in size to those in RO filters, so can they be used more often as a 
cheaper alternative to RO? Yes, mainly due to recent advances in nanotechnology. 

Nanomembranes have been around for decades, and were usually composed of a homogenous material 
throughout the fabric of the membrane. Recently, however, scientists have been able to build nanomem- 
branes in layers, inserting substances with a particular chemistry and specific purpose. For example, new 
nanomembranes can not only filter based on size but also based on charge. In other words, the membrane 
can stop very small particles with a particular electrostatic charge while allowing water through. 

Such advances have been made possible because of new tools and methods. Emphasize that engineer- 
ing membranes to be uniquely designed for a specific purpose is a characteristic of nanofiltration and 
nanotechnology in general. 

Slide 21: New Nanofilters are Unique! 

Scientists can embed noxious substances in nanomembranes — substances that will kill bacteria on contact! 
Also, channels can be built into the membranes that are surprisingly hydrophilic, attracting water to 
pass through the membrane, thus reducing the pressure needed to push the water through it. Further, 
scientists envision creating membranes that are self- cleaning: a feedback mechanism initiates a chemical 
process that removes fouling residue. Using self-cleaning membranes could reduce both maintenance and 
operating expenses. 

Benefits of nanomembranes are elaborated in more detail in the New Nanomembranes: Student Reading. 

Slide 22: New Nanomembranes I 

Eric Hoek talks about embedding particles into the membrane that are toxic to bacteria in the New 
Nanomembranes: Student Reading. When the bacteria combine with the toxic embedded substance, the 
bacteria die. 

Slide 23: New Nanomembranes II 

Two advances of new nanomembranes include the embedding of hydrophilic tubes through which water 
travels to the other side of the membrane, and the weaving of a conducting material through a membrane 
to repel oppositely charged particles. 

Slide 24: 1 nm Sized Nanopores Repel Electronegative Objects 

Eric Hoek explains this idea in the New Nanomembranes: Student Reading. This discovery was made 
serendipitously when constructing membranes with 1 to 2 nanometer pores. 

Slide 25: Nanofiltration Summary 

This slide concludes the introduction of how nanomembranes can be used to filter contaminants out of 
water. Hopefully students have gained an appreciation for how nanomembranes can be built with selected 

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properties by embedding them with specialized materials. Nanomembranes hold the promise of a new 
generation of water filtration membrane technology. 

Slide 26: Questions for Discussion 

This final slide poses further questions for discussion that are related to this lesson. You may want to ask 
students to discuss their ideas aloud or in writing, to reinforce the central concepts. 



Which Method is Best? Teacher Instructions &; Answer Key 



Purpose 

Use the Filtration Spectrum: Student Handout to determine which filtration method is best suited to filter 
a variety of particles. 

The goal is to have students actively use the information in the handout to become familiar with the 
limitations of each filtration method. This exercise will also help students visualize the transport of 
particles, and not others, through different membranes. 

Introduction and Example 

If you had a filter that was made of paper, it would not let sand pass through but would allow water and 
dissolved sodium chloride pass through. To demonstrate this, you would draw the following arrows: 



Filter Paper 



Na + 



cr 



HO 



I Sand 



Refer to the Filtration Spectrum handout. Based on what you see in the handout, draw arrows that show 
which particles will pass through each membrane and which will not. 



Microfilter 



Ultrafitter 



Nanofilter 



Reverse 
Osmosis 



Water Monovalent Multivalent Viruses Bacteria Saspendei 
Ions Ions Solids 



¥ ¥ 



i L 



Ill 



I I I I 



1 * 

I I III 



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Comparing Nanofllters to Conventional Filters Lab Activity: Teacher 
Instructions 

This lab activity demonstrates the concept of filtration as a means of separating a variety of substances from 
water using a variety of filtration techniques (Part I), and then compares ultrafiltration with nanofiltration 
(Part II). In particular, students will observe and test "river water" to identify the substances mixed 
and dissolved into the water, and then run the water through a series of filtration systems, ending with 
nanofiltration. They will perform chemical tests and make visual observations to determine if the substances 
originally identified in the water remain in solution after using various filtration techniques, and report 
their results on lab sheets. 

If you have already conducted this type of investigation using filtration, you may go directly to Part 
II, comparing ultrafiltration with nanofiltration. Rather than creating the "river water" and testing it 
according to the directions specified below, you may simply want to purchase a water-testing kit and 
collect your own sample of river water (pond water, lake water, etc.). 

The company Argonide manufactures and sells a nanofiltration kit that contains everything that you need 
for the nanofiltration activities in this lab. To purchase, contact: 

Henry Frank, Sales and Marketing Manager 

Argonide Corporation (www.argonide.com) 

291 Power Court, Sanford, FL 32771-1943 

Email: henry@argonide.com, Tel: 407-322-2500, Fax: 407-322-1144 

with this order information: 

Product #: MTK-SRI 

Description: NanoCeram Media Test Kit (complete) 

Price: 1-10 kits: $216.50/kit; 11-49 kits: $201.84/kit; 50+ kits: $187.19/kit. 

Overview 

You are on a backpacking trip in the mountains with a friend. Each of you has brought 2 liters of water 
with you and you are running very low. You had planned to stay at least for another day, but realize 
that if you don't find a source of clean drinking water, you will need to turn back and end your trip early. 
You brought with you some water testing strips and a nanofilter that fits inside of a syringe, just in case 
you needed to drink the water from the river. Your job is to use your testing strips to find out what else, 
besides what you can see (such as leaves) is in the water. Once you find what is in the water, you will have 
to filter out any of the unwanted substances. 

The pores of your nanofilter are so small that they will easily plug with large substances. You want to filter 
as much as you can using the gravel and the sand by the river in a funnel. You have also brought activated 
charcoal with you. 

Can you make the river water clean enough to drink, or do you have to turn around and go 
home? 

Materials for Each Station: Filtration (Part I) 

• 1/2 cup sand 

• 1/2 cup gravel 

• About 50 mL of activated charcoal 

• 1 25 mm NanoCeram® nanofilter disc 

• 1 Luer-Loc filter housing (to hold the nanofilter) 

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• 2 250 mL beakers 

• 1 funnel 

• Paper towels 

• Syringe 

• Test strips for nitrate and nitrite ions 

• Test strips for chloride ions 

• Test strips for copper 

• Test strips or drops for iron(II) and iron(III) ions 

• 1/2 liter of "river water" in a bottle 

Materials to Make 1.0 Liter of "River Water" for Two Lab Stations 

• 2 half-liter bottles 

• 1 liter of distilled water 

• 1/2 teaspoon salt 

• A few crushed leaves 

• 3 pinches of dirt 

• 2 pinches of sand 

• 2 teaspoons table salt 

• 2.5 mL No More Algae liquid by Jungle, 0.05% (by volume) copper sulfate pentahydrate (source of 
copper liquid) 

• 1 crushed tablet of Fe(27 mg) purchased at a drug or grocery store 

Materials for Each Station: Comparing Ultrafiltration with Nanofiltration (Part II) 

• 1 25 mm NanoCeram® nanofilter disc 

• 1 25 mm Millipore VS ultrafilter disc 

• 1 Luer-Loc filter housing (to hold the nanofilter and the ultrafilter) 

• Syringe 

• Bottle of water containing dissolved dye 

• (2) small effluent collectors 

• Paper towels 

Procedures: Filtration (Part I) 

Mix together all of the river water ingredients and pour into two half-liter bottles. 

Distribute river water and materials to each lab station, and post the student instructions at each lab 
station for students to follow. 

Each student should have their own lab sheet for recording their data and answering questions. 

Setup 

1. Put the charcoal in water to soak for at least 10 minutes, and proceed with the next step. After 
10 minutes, take the charcoal out and rinse it thoroughly to prevent coloring the water. 

2. Arrange the ring on the ring stand and put the empty funnel inside of the ring, as shown in Figure 
1. Put the 250 ml beaker underneath the funnel so it will catch the effluent. 

3. Look at the river water in the bottle. Record your observations of the river water on your lab sheet. 
Be sure to notice texture, colors, and anything else that stands out. 

4. Follow the instructions in the Ion Testing box below to test the river water for the presence of the 
ions. 

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Figure 3.78: Funnel supported by ring with beaker underneath to catch effluent [1]. 



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482 



Ion Testing 

1. Label a paper towel with each of the symbols of the ions you will test: 

Fe 2+ Fe 3+ Cl~ N0 3 ~ N0 2 ~ Cu 2+ 

2. Dip the appropriate strips in the river water to test for these ions. 

3. Put the wet strips on a paper towel under their appropriate symbols so you don't forget which strip 
represents a test for which ion. 

4. Match the color of your strip with the color chart on the side of the relevant test strip bottle. The 
amount of the ion in your river water sample will be listed underneath the matching color square on the 
bottle. 

5. Record on your lab sheet the color of the strip and the amount of each ion indicated by the test strip. 

You will repeat this "ion testing" step after each filtration to find out if the ions are still present in the 
water. 

Table 1 summarizes the consequences of the presence of these ions in drinking water. 
Table 3.21: Ions and Consequences in Drinking Water 

Ions Consequences in Drinking Water 

Fe 2+ and Fe 3+ These ions indicate that rust from pipes has got- 

ten into the water. While rust is not dangerous, 
it makes the water taste bad and leaves mineral 
deposits in sinks and bathtubs. 

NO%~ and NO2 These ions are an indication that pesticides from 

agriculture have gotten into the water. 

Cl~ This ion indicates that salt has intruded into the 

water. People cannot use salty water for drinking. 
Salty water usually cannot be used for agriculture 
either, although there are a few exceptions. 

Cu 2+ Copper is normally found in water from natural 

sources as well as from corrosion of the copper pipes 
used for water. Copper is not harmful in quantities 
less than 1000 - //m. 

Gravel Filtration 

1. Put 1/2 cup of gravel into the funnel. 

2. Put a clean 250 mL beaker underneath the funnel. 

3. Pour the river water supplied by your teacher over the gravel. Notice if the gravel stopped any of the 
substances that you saw in the water from going into the beaker below. 

4. Record your observations on your lab sheets. 
Gravel and Sand Filtration 

5. Put 1/2 cup of sand on top of the gravel in the funnel. 

6. Put a clean 250 mL beaker under the funnel. 

7. Pour the contents of the first beaker, the effluent, into the funnel on top of the sand. Notice if the sand 

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and gravel stop any of the substances in the water from going into the beaker below. 

8. Record your observations on your lab sheet. 

9. Rinse the empty 250 mL beaker and place it underneath the funnel. 
Gravel, Sand, and Activated Charcoal Filtration 

10. Put the activated charcoal into the funnel on top of the sand and the gravel. 

11. Pour the remaining water (the effluent) left from the sand filtration step into the funnel on top of the 
charcoal. Notice if the charcoal removes anything else. 

12. Record your observations on your lab sheet. 
Conduct Ion Test 

13. Using the test strips, test for the presence of the ions in the filtered water by following the instructions 
in the Ion Testing box above. 

14. Record the results of your ion tests on your lab sheet and answer the questions. 
Nanofiltration 

15. Get a 25 mm NanoCeram® nanofilter disc and a Luer-Loc ceramic filter housing. 

16. Open the filter housing and carefully place the disc into the filter housing, place the O-ring on top of 
the disc, and close securely, making sure the disc is centered in the housing to prevent leakage around the 
edges of the disc. 

17. Rinse the empty 250 mL beaker and place it underneath the filter. 

18. Fill the syringe with the effluent collected after filtering with the charcoal, sand, and gravel. 

19. Screw the filter housing onto the syringe, taking care not to depress the plunger of the syringe during 
this operation. 

20. Push the effluent through the nanofilter using even, steady pressure. 

21. Record your observations of the solution after it has gone through the nanofilter on your lab sheet. 
Conduct Ion Test 

22. Using the test strips, test for the presence of the ions in the filtered water by following the instructions 
in the Ion Testing box above. 

23. Record the results of your ion tests on your lab sheet and answer the questions. 

Procedures: Comparing Ultrafiltration with Nanofiltration (Part II) 

You have just used a new nanofilter (the NanoCeram filter) that has recently come to market. An older 
ultrafilter, called the Millipore VS filter is also available. The NanoCeram® filter is a multilevel woven 
membrane with various nanoparticles embedded into the layers of membranes. The Millipore VS membrane 
is a nonwoven, matte-like paper. 

The purpose of this part of the lab activity is to compare the anofilter with the ultrafilter based upon the 
following two criteria: 

• Completeness of filtration 

• The relative amount of pressure needed to push the water through each filter 

The completeness of filtration will be measured by filtering dissolved dye through each of the filters and 
looking at the color of the filter and the effluent. The relative pressure needed for filtration will be measured 
by how hard you have to push the syringe to get the water to pass through the filters. 

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Compare Millipore VS and NanoCeram® Filtration 

1. Open the bottle containing the dissolved dye and draw 2-3 mL into the syringe. 

2. Open the Luer-Loc filter housing and carefully place a single 25 mm disc of Millipore VS membrane 
material into it. Place the O-ring on top of the disc and close securely, making sure the disc is centered 
in the housing to prevent leakage around the edges of the disc. 

3. Screw the filter housing onto the syringe, taking care not to depress the plunger of the syringe during 
this operation. 

4. Depress plunger of the syringe while holding the syringe over an effluent collector to capture the fluid 
as it exits the syringe through the filter housing. 

5. Apply enough pressure to ensure that the dissolved dye is passing through the filter media. Typical 
results for this stage using the Millipore VS membrane material show only several drops coming out 
of the syringe due to the extreme amount of pressure required to force the dissolved dye through the 
filter. 

6. Once this is completed, carefully remove and open the filter housing, and remove the filter membrane. 

7. Place the membrane aside, next to the effluent collector containing the effluent from this test. 

8. Rinse the syringe and repeat the sequence of steps 1-7 above, but with the NanoCeram® filter. 
Push the dissolved dye through gently and steadily; avoid pushing fast. 

9. Compare the color of the effluent from the two filters, the color of the filters, and how easy or hard 
it was to push the dissolved dye through the filters with the syringe. 

10. Record your observations on your lab sheet. 

11. Answer the questions on your lab sheet. 

12. Clean your lab station. 

References 

(Accessed January 2008.) 

• http : //icn.2 . umeche .maine . edu/newnav/newnavigator/images/P7280072 . JPG 

Cleaning Jarny's Water: Teacher Instructions &; Answer Key 

This problem-solving activity is based on a real world story about the water of Jarny, France. A problem 
scenario is presented in which students use data to compare Jarny water quality (i.e. levels of substances) 
with Environmental Protection Agency fresh drinking water standards. Students will determine which 
substances need to be filtered from the water to make it safe to drink. Students are asked to design one or 
more additional water filters to make the water safe to drink for the people of Jarny. 

Students may use The Filtration Spectrum: Student Handout, which shows particle size, particle type, 
and appropriate filtration system as a resource to guide their work. It is recommended that the students 
work in heterogeneous ability groups of three or four and that they share with the class the water filtration 
systems that they have designed. 

There's a Problem with Our Water... 

In the Eastern part of France, in the city of Jarny (see Figure 1), the local people have a serious problem 
with their drinking water. Their main source of drinking water comes from the ground water table located 
near an old iron mine. (See Figure 2 for an explanation of ground water.) 

The water has always been pumped out of the mine and filtered before being used for drinking water. 
When the mine was active, this system worked fine. But since closing, the water has flooded up into the 
mine, creating a pool of standing water that seeps into the ground water used for drinking. 

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Figure 3.79: Jarny, France (green arrow) [1]. 



Over time, the water sitting in the mine reacted with the debris left in the abandoned mine, leaving much 
of the water contaminated. A local water-monitoring agency has watched the rising contamination levels 
and determined that the current water cleaning system is not good enough to make the water safe to drink. 
Even before the water flooded up into the mine, a few substances were slightly above safety limits, but 
now their levels are even higher. 




Stream 



Ccrfring j-it 



Figure 3.80: Ground water [2]. 

Water that comes from rain (precipitation) trickles through the ground (infiltration) until it flows to an 
area that it can't pass through, such as bedrock. Fresh water accumulates in these places and is referred 
to as ground water. The top of the ground water is the water table. When this underground water is large 
enough, it is called an aquifer. Aquifers are a commonly used source of fresh drinking water for people all 
over the world. 



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486 



Now that you have some background on the water problem facing Jarny, your team's job is to design a 
system to clean the water to make it drinkable by the local residents. To do this you will need to do the 
following: 

1. Analyze the data in Table 1 to identify what harmful substances are present in the water. This table 
provides raw water measurements on a set of substances, selected due to their change in concentration 
before and after the flooding. 

2. Complete question 1 in the Student Report. Record the following information for each substance: 

• The name of the substance identified to be filtered out of the water 

• The amount the substance is over the acceptable limit 

• The ranking of substances by size (1 = largest) 

• The least expensive filter needed to filter the substance identified 

3. Analyze the data on the current water cleaning system (Table 2), your reading handouts, and relevant 
charts to help inform your design of a system to clean the water to make it drinkable. Assume that your 
design will be added on to the system currently in place: a flocculation procedure, a sand filter, and a 
1.0 micron microfilter. Remember that the town is poor and your design needs to provide a cost-effective 
solution. Your design may involve single-step or multiple-step methods. 

4. Complete questions 2 and 3 in the Student Report. 





Table 3.22: 


Water 


Measurements Before and After 


Flooding 


Substance 




Before 


flooding 


After 


flooding 


"Safe" 


levels 


Health hazard or 






(mg/L) 






(mg/L) 




(mg/L) 




water-taste quality 


Ca 2+ 




168 






296 




160 




Contributes to wa- 
ter "hardness" 


Mg 2+ 




31 






185 




15 




Contributes to wa- 
ter "hardness" 


Na + 




50 






260 




350 




Dehydration 


co 3 2 ~ 




367 






500 




100 




Taste or alkalinity 


SO A 2 ~ 




192 






1794 




300 




Water taste 


Cd 2+ 




.002 






.018 




.005 




Kidney damage 


Bacteria (E. 


coli) 









24 









Diarrhea, cramps, 
nausea, or 
headaches 


Asbestos (million 


2 






12 




7 




Increased risk of 


fibers/L) from rot- 
















developing intesti- 


ting pipes 


















nal polyps 


Human hair 


(mil- 


16 






48 




3 




None known, just 


lion hairs/L) 


















disgusting 



Jarny's Current Water Cleaning System 

Jarny's current water cleaning system involves treating the water with a flocculent (a material that combines 
with large-sized particles in the water) and then letting the flocculent (with the large particle combinations) 
sink to the bottom so it can be removed. The remaining water is filtered through two filters: 1) sand, and 
then 2) a membrane with 1.0 micrometer diameter holes. 



487 



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References 

• http://maps.google.com 

• Adapted from http://ga.water.usgs.gov/edu/earthgwdecline.html 

Student Report 

1. Use the water quality information in Table 1 to fill in Table 3 below. 

Table 3.23: Substances Present at Unacceptable Levels 



Substance 



Amount over accept- 
able limit 



Rank substances by Least expensive filter 
size (1 = largest) necessary 

If there is a range, 
choose the size at the 
smallest end of the 
range Particles of sim- 
ilar size can have the 
same ranking 



Ca 2+ 




136 mg/L 




4 


nanohlter 


Mg 2+ 




170 mg/L 




4 


nanofilter 


co 3 2 ~ 




400 mg/L 




4 


nanohlter 


SO A 2 ~ 




1494 mg/L 




4 


nanohlter 


Cd 2+ 




0.013 mg/L 




4 


nanohlter 


Bacteria (E 


coli) 


24 




2 


microhlter 


Asbestos 




5 




3 


ultrahlter 


Human hair 




45 


(between 


1 


particle hlter 






40 — 300 microns) 







2. The best hlter or combination of filters to add to Jarny's water system are the following, in order: 
A ultrahlter (hlter with a pore size of < 0.1 microns) and then a nanohlter. 

3. Draw your design showing the water and its contents before and after passing through each hlter in 
your design. 



Ultra filter 
Nanofilter 


Na~ 


Ca^'.Mg^'.Cd 2 *. S0 4 2 ' 


Asbestos 

1 


Bacteria 

\ 


1 






1 


1 








1 






1 


i 









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488 



Reflecting on the Guiding Questions: Teacher Instructions 

You may want to have your students keep these in a folder to use at the end of the unit, or collect them 
after each lesson to see how your students' thinking is progressing. 

Think about the activities you just completed. What did you learn that will help you answer the guiding 
questions? Jot down notes in the spaces below. 

1. Why are water's unique properties so important for life as we know it? 
What I learned in these activities: 

What I still want to know: 

2. How do we make water safe to drink? 
What I learned in these activities: 
What I still want to know: 

3. How can nanotechnology help provide unique solutions to the water shortage? 
What I learned in these activities: 

What I still want to know: 

4. Can we solve our global water shortage problems? Why or why not? 
What I learned in these activities: 

What I still want to know: 



Image Sources 



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(2 
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(4 
(5 

(6 
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(13 

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